| Patent application number | Description | Published |
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| 20100118592 | NONVOLATILE SEMICONDUCTOR MEMORY DEVICE AND METHOD OF CONTROLLING THE SAME - Provided is a nonvolatile semiconductor memory device capable of performing a writing action for a memory cell at high speed. The device comprises: a memory cell array having a first sub-bank and a second sub-bank each having a plurality of nonvolatile memory cells arranged in a form of a matrix; a row decoder shared by the first sub-bank and the second sub-bank; a first column decoder and a second column decoder provided in the first sub-bank and the second sub-bank, respectively; and a control circuit arranged to execute alternately a first action cycle to perform a programming action in the first sub-bank and a reading action for a programming verifying action in the second sub-bank and a second action cycle to perform the reading action for the programming verifying action in the first sub-bank and the programming action in the second sub-bank. | 05-13-2010 |
| 20100232209 | CONTROL CIRCUIT FOR FORMING PROCESS ON NONVOLATILE VARIABLE RESISTIVE ELEMENT AND CONTROL METHOD FOR FORMING PROCESS - A nonvolatile semiconductor memory device can carry out a forming process simultaneously on the nonvolatile variable resistive elements of memory cells and make the forming time shorter. The nonvolatile semiconductor memory device has a forming detection circuit provided between the memory cell array and the second selection line (bit line) decoder. The forming detection circuit detects the completion of the forming process for memory cells by measuring the fluctuation in the potential of second selection lines or the current flowing through the second selection lines when applying a voltage pulse for a forming process through the second selection lines simultaneously to the memory cells on which a forming process is to be carried out connected to the same first selection line (word line), and prevents a voltage from being applied to the second selection lines connected to the memory cells where the completion of the forming process is detected. | 09-16-2010 |
| 20110228586 | NONVOLATILE SEMICONDUCTOR MEMORY DEVICE - A nonvolatile semiconductor memory device includes a bit voltage adjusting circuit which, for each bit line, fixes potentials of a selected bit line and a non-selected bit line to a predetermined potential to perform a memory operation and a data voltage adjusting circuit which, for each data line, fixes potentials of a selected data line and a non-selected data line to a predetermined potential to perform a memory operation. Each of the voltage adjusting circuits includes an operational amplifier and a transistor, a voltage required for a memory operation is input to the non-inverted input terminal of the operational amplifier, and the inverted input terminal of the operational amplifier is connected to the bit line or the data line, so that the potential of the bit line or the data line is fixed to a potential of the non-inverted input terminal of the operational amplifier. | 09-22-2011 |
| 20110292715 | SEMICONDUCTOR MEMORY DEVICE - A semiconductor memory device includes a memory cell array in which a plurality of memory cells is aligned in a matrix shape, each memory cell including a two-terminal memory element and a transistor for selection connected in series; a first voltage applying circuit that applies a writing voltage pulse to first bit lines; and a second voltage applying circuit that applies a pre-charge voltage to the first bit lines and second bit lines, wherein in a writing of a memory cell, after the second voltage applying circuit has pre-charged both ends of the memory cell to a same voltage, the first voltage applying circuit applies the writing voltage pulse via the first bit line that is directly connected to the transistor for selection, and the second voltage applying circuit applies the pre-charge voltage to the second bit line directly connected to the memory element. | 12-01-2011 |
| 20110305070 | RESISTANCE CONTROL METHOD FOR NONVOLATILE VARIABLE RESISTIVE ELEMENT - A resistance control method for a nonvolatile variable resistive element in a nonvolatile semiconductor memory device is provided. The device includes a memory cell array in which unit memory cells having nonvolatile variable resistive elements and transistors are arranged in a matrix. The memory cells that are targets of a memory operation are selected by first selection lines (word lines), second selection lines (bit lines) and third selection lines (source lines). The method includes steps of selecting one or more first selection lines, selecting a plurality of second selection lines, and applying a compensated voltage in which a change in potential of the third selection lines caused by current flowing into the third selection lines through the second selection lines is compensated in a voltage that is necessary for the memory operation, such that the voltage necessary for the memory operation is applied to all of the selected memory cells. | 12-15-2011 |
| 20120014163 | SEMICONDUCTOR MEMORY DEVICE AND METHOD OF DRIVING THE SAME - A semiconductor memory device includes a memory cell array where a plurality of memory cells are arranged in a matrix, each of the memory cells serially connecting a two-terminal type memory element and a transistor for selection, a first voltage applying circuit that applies a write voltage pulse to a bit line, and a second voltage applying circuit that applies a precharge voltage to a bit line and a common line. In writing the memory cell, after the second voltage applying circuit has both terminals of the memory cell previously precharged to the same voltage, the first voltage applying circuit applies the write voltage pulse to one terminal of the writing target memory cell via the bit line, and while the write voltage pulse is applied, the second voltage applying circuit maintains the application of the precharge voltage to the other terminal of the memory cell via the common line. | 01-19-2012 |
| 20120025163 | NON-VOLATILE SEMICONDUCTOR DEVICE - A variable resistance element that can stably perform a switching operation with a property variation being reduced by suppressing a sharp current that accompanies completion of forming process, and a non-volatile semiconductor memory device including the variable resistance element are realized. The non-volatile semiconductor memory device uses the variable resistance element for storing information in which a resistance changing layer is interposed between a first electrode and a second electrode, and a buffer layer is inserted between the first electrode and the resistance changing layer where a switching interface is formed. The buffer layer and the resistance changing layer include n-type metal oxides, and materials of the buffer layer and the resistance changing layer are selected such that energy at a bottom of a conduction band of the n-type metal oxide configuring the buffer layer is lower than that of the n-type metal oxide configuring the resistance changing layer. | 02-02-2012 |
| 20120075909 | SEMICONDUCTOR MEMORY DEVICE - Provided is a semiconductor memory device that is capable of stably programming with desirable controllability to a desired electric resistance state in a random access programming action and is provided with a variable resistance element. Regardless of a resistance state of a variable resistance element of a memory cell that is a target of a writing action (erasing and programming actions), an erasing voltage pulse for bringing the resistance state of the variable resistance element to an erased state having a lowest resistance value is applied. Thereafter, a programming voltage pulse for bringing the resistance state of the variable resistance element to a desired programmed state is applied to the variable resistance element of the programming action target memory cell. By always applying the programming voltage pulse after having applied the erasing voltage pulse, a plurality of programming voltage pulses being sequentially applied can be avoided. | 03-29-2012 |
| 20120075911 | SEMICONDUCTOR MEMORY DEVICE - Regardless of a resistance state of a variable resistance element of a memory cell that is a target of a writing action (erasing and programming actions), an erasing voltage pulse for bringing the resistance state of the variable resistance element to an erased state having a lowest resistance value is applied. Thereafter, a programming voltage pulse for bringing the resistance state of the variable resistance element to a desired programmed state is applied to the variable resistance element of the programming action target memory cell. By always applying the programming voltage pulse after having applied the erasing voltage pulse, a plurality of programming voltage pulses being sequentially applied can be avoided. Further, the memory cell array is constituted of even-numbers of subbanks, and the application of the erasing voltage pulse in one subbank and the application of the programming voltage pulse in the other subbank are alternately performed. | 03-29-2012 |
| 20120081946 | NONVOLATILE SEMICONDUCTOR MEMORY DEVICE - A nonvolatile semiconductor memory device includes a memory cell array for storing user data provided by arranging memory cells each having a variable resistive element having a first electrode, a second electrode, and a variable resistor made of a metal oxide sandwiched between the first and second electrodes. The first and second electrodes are formed of a conductive material forming ohmic junction with the variable resistor and a conductive material forming non-ohmic junction with the variable resistor, respectively. The variable resistor changes between two or more different resistance states by applying a voltage between the electrodes. The resistance state after being changed is maintained in a nonvolatile manner. The variable resistive elements of all memory cells in the memory cell array are set to the highest of the two or more different resistance states in an unused state before the memory cell array is used to store the user data. | 04-05-2012 |
| 20120266043 | SEMICONDUCTOR MEMORY DEVICE - The invention realizes a semiconductor memory device that can efficiently execute a detection of a data error that might possibly occur in a continuous reading action, and a correction of the error data. The semiconductor memory device uses a variable resistive element made of a metal oxide for storing information. During a reading action of coded data with an ECC in the semiconductor memory device, when a data error is detected by an ECC circuit, a writing voltage pulse having a polarity opposite to a polarity of a reading voltage pulse is applied to all memory cells from which the error is detected so as to correct bits from which the error is detected, on an assumption that an erroneous writing has occurred due to the application of the writing voltage pulse having the polarity same as the polarity of the applied reading voltage pulse. | 10-18-2012 |
| 20120297268 | NONVOLATILE SEMICONDUCTOR MEMORY DEVICE - The present invention provides a nonvolatile semiconductor memory device that can optimize a timing of performing an error detection and correction process to shorten a processing time. Upon receiving a write request to a memory cell array including a variable resistive element where information is stored based on a resistance state of a variable resistor, an input/output buffer outputs write data to a write control unit and an ECC control unit. The write control unit performs a data write process of writing divided data, obtained by dividing the write data into a predetermined number of data, to the databanks. The ECC control unit generates a first error correction code by performing an error correction code generation process to the write data or the divided data, in parallel with the data write process. The write control unit performs a code write process of writing first test data into an ECC bank. | 11-22-2012 |
| 20120300532 | METHOD OF FORMING PROCESS FOR VARIABLE RESISTIVE ELEMENT AND NON-VOLATILE SEMICONDUCTOR MEMORY DEVICE - A method of a forming process for a variable resistive element, which is performed in short time comparable to the pulse forming and a writing current in a switching action is the same level as that of the DC forming, is provided. In the forming process, a variable resistive element is changed by voltage pulse application from an initial high resistance state just after produced to a variable resistance state where the switching action is performed. The forming process includes a first step of applying a first pulse having a voltage amplitude lower than a threshold voltage at which the resistance of the variable resistive element is lowered, to between both electrodes of the variable resistive element, and a second step of applying a second pulse having a voltage amplitude having the same polarity as the first pulse and not lower than the threshold voltage, thereto after the first step. | 11-29-2012 |
| 20120314480 | SEMICONDUCTOR MEMORY DEVICE - In a semiconductor memory device using a variable resistive element made of a metal oxide for storing information, a voltage amplitude of a writing voltage pulse for changing the variable resistive element to a high resistance state is set within a voltage range in which the resistance value of the high resistance state after the change increases with time. The voltage amplitude is set within the voltage range in which the resistance value of the high resistance state after the change increases toward a predetermined peak with increase in voltage amplitude. When a data error is detected by the ECC circuit, it is estimated that the data that should be in the low resistance state changes to the high resistance state, and the variable resistive elements of all memory cells from which the error is detected are written to the low resistance state to correct the error bit. | 12-13-2012 |
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| 20090096568 | VARIABLE RESISTANCE ELEMENT, AND ITS MANUFACTURING METHOD - Provided are a variable resistive element having a configuration that the area of an electrically contributing region in a variable resistor body is smaller than the area defined by an upper electrode or a lower electrode, and a method for manufacturing the variable resistive element. The cross section of a current path, in which an electric current flows through between the two electrodes via the variable resistor body at the time of applying the voltage pulse to between the two electrodes, is formed with a line width of narrower than that of any of the two electrodes and of smaller than a minimum work dimension regarding manufacturing processes, so that its area can be made smaller than that of the electrically contributing region in the variable resistive element of the prior art. | 04-16-2009 |
| 20090102597 | VARIABLE RESISTANCE ELEMENT - In a variable resistance element having a variable resistor between first and second electrodes and changing its electric resistance when a voltage pulse is applied between both electrodes, data holding characteristics can be improved by increasing a programming voltage and programming in a high current density. Therefore, a booster circuit for supplying a high voltage is needed when the variable resistance element is applied to a nonvolatile memory. When the smaller of the areas of the contact regions between the first electrode and variable resistor and between the second electrode and variable resistor is set to the electrode area of the variable resistance element, it is set within a specific range not larger than the predetermined electrode area. Thereby the programming current density can be increased without raising the programming voltage, and the variable resistance element having preferable data holding characteristics even at a high temperature can be provided. | 04-23-2009 |
| 20090200640 | VARIABLE RESISTIVE ELEMENT, AND ITS MANUFACTURING METHOD - A variable resistive element comprising a configuration that an area of an electrically contributing region of a variable resistor body is finer than that constrained by an upper electrode or a lower electrode and its manufacturing method are provided. A bump electrode material is formed on a lower electrode arranged on a base substrate. The bump electrode material is contacted to a variable resistor body at a surface different from a contact surface to the lower electrode. The variable resistor body is contacted to an upper electrode at a surface different from a contact surface to the bump electrode material. Thus, a cross point region between the bump electrode material (the variable resistor body) and the upper electrode becomes an electrically contributing region of the variable resistor body, and then an area thereof can be reduced compared with that of the region regarding the conventional variable resistive element. | 08-13-2009 |
