Patent application number | Description | Published |
20080258822 | OSCILLATOR CIRCUIT AND SEMICONDUCTOR DEVICE INCLUDING THE SAME - A stable frequency is outputted by an oscillator circuit including a constant current circuit which is electrically connected between a first terminal and a second terminal, a voltage controlled oscillator circuit in which an oscillation frequency fluctuates in accordance with a potential difference between power supply voltage terminals, an n-channel transistor, a p-channel transistor in which a gate-source voltage is set to be constant by the constant current circuit, and a capacitor, in which a source electrode of the p-channel transistor is electrically connected to the first terminal, a drain electrode of the p-channel transistor is electrically connected a drain electrode and a gate electrode of the n-channel transistor, a source electrode of the n-channel transistor is electrically connected to the second terminal, and a gate electrode of the n-channel transistor is electrically connected to the second terminal through the capacitor. | 10-23-2008 |
20090302481 | SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD THEREOF - The invention provides a technology for manufacturing a higher performance and higher reliability semiconductor device at low cost and with high yield. The semiconductor device of the invention has a first conductive layer over a first insulating layer; a second insulating layer over the first conductive layer, which includes an opening extending to the first conductive layer; and a signal wiring layer for electrically connecting an integrated circuit portion to an antenna and a second conductive layer adjacent to the signal wiring layer, which are formed over the second insulating layer. The second conductive layer is in contact with the first conductive layer through the opening, and the first conductive layer overlaps the signal wiring layer with the second insulating layer interposed therebetween. | 12-10-2009 |
20100085792 | Semiconductor Device - A semiconductor device including a memory cell is provided. The memory cell comprises a transistor and a capacitor, and one of a resistor and a diode. A gate of the transistor is electrically connected to a word line, and one of a source and a drain of the transistor is electrically connected to a bit line. One terminal of the capacitor is electrically connected to the other of the source and the drain of the transistor, and the other terminal of the capacitor is electrically connected to a wiring. One terminal of one of the resistor and the diode is electrically connected to the other of the source and the drain of the transistor, and the other terminal of one of the resistor and the diode is electrically connected to the wiring. | 04-08-2010 |
20100181384 | Semiconductor Device - A semiconductor device which stores data, and in which refresh operation is not needed, is described. The semiconductor device comprises at least a transistor and a capacitor. A first electrode of the capacitor is connected to a reference voltage terminal and a second electrode of the capacitor is connected to one of a source and a drain of the transistor. The semiconductor device is configured to put, when necessary, the other of the source and the drain of the transistor to the same potential as the one of the source and the drain, so that charge accumulated in the capacitor, which is connected to the one of the source and the drain of the transistor, does not leak through the transistor. | 07-22-2010 |
20100266070 | SEMICONDUCTOR DEVICE - A semiconductor device is provided, which comprises a first demodulation circuit, a second demodulation circuit, a first bias circuit, a second bias circuit, a comparator, an analog buffer circuit, and a pulse detection circuit. An input portion of the pulse detection circuit is electrically connected to an output portion of the analog buffer circuit, a first output portion of the pulse detection circuit is electrically connected to an input portion of the first bias circuit, and a second output portion of the pulse detection circuit is electrically connected to an input portion of the second bias circuit. | 10-21-2010 |
20110080774 | SEMICONDUCTOR DEVICE - Objects of the present invention are to improve the manufacturing yield of semiconductor devices, reduce manufacturing cost of the semiconductor device, and reduce the circuit area of an integrated circuit included in the semiconductor device. A memory layer of a memory element and a resistive layer of a resistor included in the semiconductor device are formed of the same material. Therefore, the memory layer and the resistive layer are formed in the same step, whereby the number of manufacturing steps of the semiconductor device can be reduced. As a result, the manufacturing yield of the semiconductor devices can be improved and the manufacturing cost can be reduced. In addition, the semiconductor device includes a resistor having a resistive component which has high resistance value. Consequently, the area of the integrated circuit included in the semiconductor device can be reduced. | 04-07-2011 |
20110156028 | SEMICONDUCTOR DEVICE - The semiconductor device includes a source line, a bit line, a signal line, a word line, memory cells connected in parallel between the source line and the bit line, a first driver circuit electrically connected to the source line and the bit line through switching elements, a second driver circuit electrically connected to the source line through a switching element, a third driver circuit electrically connected to the signal line, and a fourth driver circuit electrically connected to the word line. The memory cell includes a first transistor including a first gate electrode, a first source electrode, and a first drain electrode, a second transistor including a second gate electrode, a second source electrode, and a second drain electrode, and a capacitor. The second transistor includes an oxide semiconductor material. | 06-30-2011 |
20110198593 | SEMICONDUCTOR DEVICE - A semiconductor device with a novel structure in which stored data can be held even when power is not supplied and there is no limitation on the number of times of writing. In the semiconductor device, a plurality of memory cells each including a first transistor, a second transistor, and a capacitor is provided in matrix and a wiring (also called a bit line) for connecting one memory cell to another memory cell and a source or drain electrode of the first transistor are electrically connected to each other through a source or drain electrode of the second transistor. Accordingly, the number of wirings can be smaller than that in the case where the source or drain electrode of the first transistor and the source or drain electrode of the second transistor are connected to different wirings. Thus, the degree of integration of the semiconductor device can be increased. | 08-18-2011 |
20110199807 | SEMICONDUCTOR DEVICE AND METHOD FOR DRIVING THE SAME - A semiconductor device includes a first signal line, a second signal line, a memory cell, and a potential converter circuit. The memory cell includes a first transistor including a first gate electrode, a first source electrode, a first drain electrode, and a first channel formation region; a second transistor including a second gate electrode, a second source electrode, a second drain electrode, and a second channel formation region; and a capacitor. The first channel formation region and the second channel formation region include different semiconductor materials. The second drain electrode, one electrode of the capacitor, and the first gate electrode are electrically connected to one another. The second gate electrode is electrically connected to the potential converter circuit through the second signal line. | 08-18-2011 |
20110199816 | SEMICONDUCTOR DEVICE AND DRIVING METHOD OF THE SAME - An object is to provide a semiconductor device with a novel structure in which stored data can be held even when power is not supplied, and the number of times of writing is not limited. The semiconductor device is formed using a wide gap semiconductor and includes a potential change circuit which selectively applies a potential either equal to or different from a potential of a bit line to a source line. Thus, power consumption of the semiconductor device can be sufficiently reduced. | 08-18-2011 |
20110204968 | DEMODULATION CIRCUIT AND RFID TAG INCLUDING THE DEMODULATION CIRCUIT - An object is to provide a demodulation circuit having a sufficient demodulation ability. Another object is to provide an RFID tag which uses a demodulation circuit having a sufficient demodulation ability. A material which enables a reverse current to be small enough, for example, an oxide semiconductor material, which is a wide bandgap semiconductor, is used in part of a transistor included in a demodulation circuit. By using the semiconductor material which enables a reverse current of a transistor to be small enough, a sufficient demodulation ability can be secured even when an electromagnetic wave having a high amplitude is received. | 08-25-2011 |
20110205775 | SEMICONDUCTOR DEVICE - An object is to provide a semiconductor device with a novel structure, which can hold stored data even when not powered and which has an unlimited number of write cycles. A semiconductor device is formed using a material capable of sufficiently reducing the off-state current of a transistor, such as an oxide semiconductor material that is a widegap semiconductor. The use of a semiconductor material capable of sufficiently reducing the off-state current of a transistor allows data to be held for a long time. In addition, the timing of potential change in a signal line is delayed relative to the timing of potential change in a write word line. This makes it possible to prevent a data writing error. | 08-25-2011 |
20110205785 | SEMICONDUCTOR DEVICE AND DRIVING METHOD OF SEMICONDUCTOR DEVICE - An object is to provide a semiconductor device with a novel structure, which can hold stored data even when not powered and which has an unlimited number of write cycles. A semiconductor device includes a memory cell including a widegap semiconductor, for example, an oxide semiconductor and the semiconductor device includes a potential conversion circuit which functions to output a potential lower than a reference potential for reading data from the memory cell. With the use of a widegap semiconductor, a semiconductor device capable of sufficiently reducing the off-state current of a transistor included in a memory cell and capable of holding data for a long time can be provided. | 08-25-2011 |
20110227072 | SEMICONDUCTOR DEVICE - A semiconductor device including a nonvolatile memory cell including a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor is provided. Data is written to the memory cell by turning on the writing transistor and supplying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected to each other, and then turning off the writing transistor so that a predetermined amount of charge is held at the node. Further, when a p-channel transistor is used as the reading transistor, a reading potential is a positive potential. | 09-22-2011 |
20110254600 | PHASE LOCKED LOOP, SEMICONDUCTOR DEVICE, AND WIRELESS TAG - An object is to provide a PLL having a wide operating range. Another object is to provide a semiconductor device or a wireless tag which has a wide operating range in a communication distance or temperature by incorporating such a PLL. The semiconductor device or the wireless tag includes a first divider circuit; a second divider circuit; a phase comparator circuit to which an output of the first divider circuit and an output of the second divider circuit are provided; a loop filter to which an output of the phase comparator circuit is supplied and in which a time constant is switched in accordance with an inputted signal; and a voltage controlled oscillator circuit to which an output of the loop filter is supplied and which supplies an output to the second divider circuit. | 10-20-2011 |
20110255325 | SEMICONDUCTOR DEVICE - An object is to provide a semiconductor device having a novel structure, which can hold stored data even when not powered and which has an unlimited number of write cycles. A semiconductor device includes a memory cell including a widegap semiconductor, for example, an oxide semiconductor. The memory cell includes a writing transistor, a reading transistor, and a selecting transistor. Using a widegap semiconductor, a semiconductor device capable of sufficiently reducing the off-state current of a transistor included in a memory cell and holding data for a long time can be provided. | 10-20-2011 |
20110280061 | SEMICONDUCTOR DEVICE - A semiconductor device includes a plurality of memory cells including a first transistor and a second transistor, a reading circuit including an amplifier circuit and a switch element, and a refresh control circuit. A first channel formation region and a second channel formation region contain different materials as their respective main components. A first gate electrode is electrically connected to one of a second source electrode and a second drain electrode. The other of the second source electrode and the second drain electrode is electrically connected to one of input terminals of the amplifier circuit. An output terminal of the amplifier circuit is connected to the other of the second source electrode and the second drain electrode through the switch element. The refresh control circuit is configured to control whether the switch element is turned on or off. | 11-17-2011 |
20120012845 | SEMICONDUCTOR DEVICE - A semiconductor device with a novel structure is provided, which can hold stored data even when no power is supplied and which has no limitations on the number of writing operations. A semiconductor device is formed using a material which enables off-state current of a transistor to be reduced significantly; e.g., an oxide semiconductor material which is a wide-gap semiconductor. With use of a semiconductor material which enables off-state current of a transistor to be reduced significantly, the semiconductor device can hold data for a long period. In a semiconductor device with a memory cell array, parasitic capacitances generated in the nodes of the first to the m-th memory cells connected in series are substantially equal, whereby the semiconductor device can operate stably. | 01-19-2012 |
20120014157 | SEMICONDUCTOR DEVICE - A plurality of memory cells included in a memory cell array are divided into a plurality of blocks every plural rows. A common bit line is electrically connected to the divided bit lines through selection transistors in the blocks. One of the memory cells includes a first transistor, a second transistor, and a capacitor. The first transistor includes a first channel formation region. The second transistor includes a second channel formation region. The first channel formation region includes a semiconductor material different from the semiconductor material of the second channel formation region. | 01-19-2012 |
20120025064 | OPTICAL SENSOR DEVICE AND ELECTRONIC APPARATUS - In an optical sensor device employing an amorphous silicon photodiode, an external amplifier IC and the like are required due to low current capacity of the sensor element in order to improve the load driving capacity. It to increase in cost and mounting space of the optical sensor device. In addition, noise may easily superimpose since the photodiode and the amplifier IC are connected to each other over a printed circuit board. According to the invention, an amorphous silicon photodiode and an amplifier configured by a thin film transistor are formed integrally over a substrate so that the load driving capacity is improved while reducing cost and mounting space. Superimposing noise can also be reduced. | 02-02-2012 |
20120025284 | Semiconductor Device - A semiconductor device includes a material with which off-state current of a transistor can be sufficiently small; for example, an oxide semiconductor material is used. Further, transistors of memory cells of the semiconductor device, which include an oxide semiconductor material, are connected in series. Further, the same wiring (the j-th word line (j is a natural number greater than or equal to 2 and less than or equal to m)) is used as a wiring electrically connected to one of terminals of a capacitor of the j-th memory cell and a wiring electrically connected to a gate terminal of a transistor, in which a channel is formed in an oxide semiconductor layer, of the (j−1)-th memory cell. Therefore, the number of wirings per memory cell and the area occupied by one memory cell are reduced. | 02-02-2012 |
20120033484 | SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF - The semiconductor device is formed using a material which allows a sufficient reduction in off-state current of a transistor; for example, an oxide semiconductor material, which is a wide gap semiconductor, is used. When a semiconductor material which allows a sufficient reduction in off-state current of a transistor is used, the semiconductor device can hold data for a long period. In addition, the timing of potential change in a signal line is delayed relative to the timing of potential change in a write word line. This makes it possible to prevent a data writing error. | 02-09-2012 |
20120033485 | SEMICONDUCTOR DEVICE - In a semiconductor device which includes a bit line, m (m is a natural number of 3 or more) word lines, a source line, m signal lines, first to m-th memory cells, and a driver circuit, the memory cell includes a first transistor and a second transistor for storing electrical charge accumulated in a capacitor, and the second transistor includes a channel formed in an oxide semiconductor layer. In the semiconductor device, the driver circuit generates a signal to be output to a (j−1)th (j is a natural number of 3 or more) signal line with the use of a signal to be output to a j-th signal line. | 02-09-2012 |
20120033486 | SEMICONDUCTOR DEVICE AND METHOD FOR DRIVING SEMICONDUCTOR DEVICE - It is an object to provide a semiconductor device with a novel structure in which stored data can be held even when power is not supplied, and does not have a limitation on the number of writing operations. A semiconductor device includes a plurality of memory cells each including a transistor including a first semiconductor material, a transistor including a second semiconductor material that is different from the first semiconductor material, and a capacitor, and a potential switching circuit having a function of supplying a power supply potential to a source line in a writing period. Thus, power consumption of the semiconductor device can be sufficiently suppressed. | 02-09-2012 |
20120033487 | SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF - A semiconductor device including a nonvolatile memory cell in which a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor are included is provided. Data is written to the memory cell by turning on the writing transistor and applying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected, and then turning off the writing transistor, so that the predetermined amount of charge is held in the node. Further, when a p-channel transistor is used as the reading transistor, a reading potential is a positive potential. | 02-09-2012 |
20120033488 | SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF - A semiconductor device including a memory cell formed using a wide bandgap semiconductor, for example, an oxide semiconductor is provided. The semiconductor device includes a potential change circuit having a function of outputting a potential lower than a reference potential for reading data from the memory cell. With the use of the wide bandgap semiconductor, an off-state current of a transistor included in the memory cell can be sufficiently reduced, and the semiconductor device which can hold data for a long period can be provided. | 02-09-2012 |
20120033510 | SEMICONDUCTOR DEVICE - An object is to provide a semiconductor device with a novel structure, which can hold stored data even when power is not supplied and which has an unlimited number of write cycles. The semiconductor device is formed using a memory cell including a wide band gap semiconductor such as an oxide semiconductor. The semiconductor device includes a potential change circuit having a function of outputting a potential lower than a reference potential for reading data from the memory cell. When the wide band gap semiconductor which allows a sufficient reduction in of state current of a transistor included in the memory cell is used, a semiconductor device which can hold data for a long period can be provided. | 02-09-2012 |
20120056647 | SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF - The semiconductor device includes a memory cell including a first transistor including a first channel formation region, a first gate electrode, and first source and drain regions; a second transistor including a second channel formation region provided so as to overlap with at least part of either of the first source region or the first drain region, a second source electrode, a second drain electrode electrically connected to the first gate electrode, and a second gate electrode; and an insulating layer provided between the first transistor and the second transistor. In a period during which the second transistor needs in an off state, at least when a positive potential is supplied to the first source region or the first drain region, a negative potential is supplied to the second gate electrode. | 03-08-2012 |
20120063203 | DRIVING METHOD OF SEMICONDUCTOR DEVICE - A driving method of a semiconductor device is provided. In a semiconductor device including a bit line, a selection line, a selection transistor, m (m is a natural number greater than or equal to 2) writing word lines, m reading word lines, a source line, and first to m-th memory cells, each memory cell includes a first transistor and a second transistor that holds charge accumulated in a capacitor. The second transistor includes a channel formed in an oxide semiconductor layer. In a driving method of a semiconductor device having the above structure, when writing to a memory cell is performed, the first transistor is turned on so that a first source terminal or a first drain terminal is set to a fixed potential; thus, a potential is stably written to the capacitor. | 03-15-2012 |
20120063205 | SEMICONDUCTOR DEVICE - A semiconductor device in which stored data can be held even when power is not supplied and there is no limitation on the number of writing operations is provided. A semiconductor device is formed using a material which can sufficiently reduce the off-state current of a transistor, such as an oxide semiconductor material that is a wide-gap semiconductor. When a semiconductor material which can sufficiently reduce the off-state current of a transistor is used, the semiconductor device can hold data for a long period. In addition, by providing a capacitor or a noise removal circuit electrically connected to a write word line, a signal such as a short pulse or a noise input to a memory cell can be reduced or removed. Accordingly, a malfunction in which data written into the memory cell is erased when a transistor in the memory cell is instantaneously turned on can be prevented. | 03-15-2012 |
20120236621 | Semiconductor Device - A semiconductor device including a memory cell is provided. The memory cell comprises a transistor and a capacitor, and one of a resistor and a diode. A gate of the transistor is electrically connected to a word line, and one of a source and a drain of the transistor is electrically connected to a bit line. One terminal of the capacitor is electrically connected to the other of the source and the drain of the transistor, and the other terminal of the capacitor is electrically connected to a wiring. One terminal of one of the resistor and the diode is electrically connected to the other of the source and the drain of the transistor, and the other terminal of one of the resistor and the diode is electrically connected to the wiring. | 09-20-2012 |
20120269013 | SIGNAL PROCESSING CIRCUIT - A signal processing circuit including a nonvolatile storage circuit with a novel structure. The signal processing circuit includes a circuit that is supplied with a power supply voltage and has a first node to which a first high power supply potential is applied, and a nonvolatile storage circuit for holding a potential of the first node. The nonvolatile storage circuit includes a transistor whose channel is formed in an oxide semiconductor layer, and a second node that is brought into a floating state when the transistor is turned off. A second high power supply potential or a ground potential is input to a gate of the transistor. When the power supply voltage is not supplied, the ground potential is input to the gate of the transistor and the transistor is kept off. The second high power supply potential is higher than the first high power supply potential. | 10-25-2012 |
20120286268 | DEMODULATION CIRCUIT AND RFID TAG INCLUDING THE DEMODULATION CIRCUIT - An object is to provide a demodulation circuit having a sufficient demodulation ability. Another object is to provide an RFID tag which uses a demodulation circuit having a sufficient demodulation ability. A material which enables a reverse current to be small enough, for example, an oxide semiconductor material, which is a wide bandgap semiconductor, is used in part of a transistor included in a demodulation circuit. By using the semiconductor material which enables a reverse current of a transistor to be small enough, a sufficient demodulation ability can be secured even when an electromagnetic wave having a high amplitude is received. | 11-15-2012 |
20120294061 | WORD LINE DIVIDER AND STORAGE DEVICE - A word line divider which has a simplified circuit structure and can operate stably is provided. A storage device which has a simplified circuit structure and can operate stably is provided. A transistor whose leakage current is extremely low is connected in series with a portion between a word line and a sub word line so that the word line divider is constituted. The transistor can include an oxide semiconductor for a semiconductor layer in which a channel is formed. Such a word line divider whose circuit structure is simplified is used in the storage device. | 11-22-2012 |
20120294070 | METHOD FOR DRIVING SEMICONDUCTOR DEVICE - A semiconductor device includes a nonvolatile memory cell including a writing transistor including an oxide semiconductor, a reading transistor including a semiconductor material different from that of the writing transistor, and a capacitor. Data is written to the memory cell by turning on the writing transistor so that a potential is supplied to a node where a source electrode of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected, and then turning off the writing transistor so that a predetermined potential is held in the node. Data is read out from the memory cell by supplying a precharge potential to a bit line, stopping the supply of the potential to the bit line, and determining whether the potential of the bit line is kept at the precharge potential or decreased. | 11-22-2012 |
20130181216 | SEMICONDUCTOR DEVICE - A semiconductor device includes a plurality of memory cells including a first transistor and a second transistor, a reading circuit including an amplifier circuit and a switch element, and a refresh control circuit. A first channel formation region and a second channel formation region contain different materials as their respective main components. A first gate electrode is electrically connected to one of a second source electrode and a second drain electrode. The other of the second source electrode and the second drain electrode is electrically connected to one of input terminals of the amplifier circuit. An output terminal of the amplifier circuit is connected to the other of the second source electrode and the second drain electrode through the switch element. The refresh control circuit is configured to control whether the switch element is turned on or off. | 07-18-2013 |
20130228838 | SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF - A semiconductor device including a nonvolatile memory cell in which a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor are included is provided. Data is written to the memory cell by turning on the writing transistor and applying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected, and then turning off the writing transistor, so that the predetermined amount of charge is held in the node. Further, when a p-channel transistor is used as the reading transistor, a reading potential is a positive potential. | 09-05-2013 |
20130256771 | SEMICONDUCTOR DEVICE - The semiconductor device includes a source line, a bit line, a signal line, a word line, memory cells connected in parallel between the source line and the bit line, a first driver circuit electrically connected to the source line and the bit line through switching elements, a second driver circuit electrically connected to the source line through a switching element, a third driver circuit electrically connected to the signal line, and a fourth driver circuit electrically connected to the word line. The memory cell includes a first transistor including a first gate electrode, a first source electrode, and a first drain electrode, a second transistor including a second gate electrode, a second source electrode, and a second drain electrode, and a capacitor. The second transistor includes an oxide semiconductor material. | 10-03-2013 |
20130301367 | SEMICONDUCTOR DEVICE - An object is to provide a semiconductor device with a novel structure, which can hold stored data even when power is not supplied and which has an unlimited number of write cycles. The semiconductor device is formed using a memory cell including a wide band gap semiconductor such as an oxide semiconductor. The semiconductor device includes a potential change circuit having a function of outputting a potential lower than a reference potential for reading data from the memory cell. When the wide band gap semiconductor which allows a sufficient reduction in off-state current of a transistor included in the memory cell is used, a semiconductor device which can hold data for a long period can be provided. | 11-14-2013 |
20130314152 | DEMODULATION CIRCUIT AND RFID TAG INCLUDING THE DEMODULATION CIRCUIT - An object is to provide a demodulation circuit having a sufficient demodulation ability. Another object is to provide an RFID tag which uses a demodulation circuit having a sufficient demodulation ability. A material which enables a reverse current to be small enough, for example, an oxide semiconductor material, which is a wide bandgap semiconductor, is used in part of a transistor included in a demodulation circuit. By using the semiconductor material which enables a reverse current of a transistor to be small enough, a sufficient demodulation ability can be secured even when an electromagnetic wave having a high amplitude is received. | 11-28-2013 |
20140264521 | SEMICONDUCTOR DEVICE - A semiconductor device in which stored data can be held even when power is not supplied and there is no limitation on the number of writing operations is provided. A semiconductor device is formed using a material which can sufficiently reduce the off-state current of a transistor, such as an oxide semiconductor material that is a wide-gap semiconductor. When a semiconductor material which can sufficiently reduce the off-state current of a transistor is used, the semiconductor device can hold data for a long period. In addition, by providing a capacitor or a noise removal circuit electrically connected to a write word line, a signal such as a short pulse or a noise input to a memory cell can be reduced or removed. Accordingly, a malfunction in which data written into the memory cell is erased when a transistor in the memory cell is instantaneously turned on can be prevented. | 09-18-2014 |