Patents by Inventor Yasuji Koshikawa
Yasuji Koshikawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 7075852Abstract: In a sub word driver circuit in a semiconductor memory device of a hierarchy word structure using a main word line signal and a sub word line signal, a first NMOS transistor and a first PMOS transistor are connected in series. A second NMOS transistor is connected with a node between the first PMOS transistor and the first NMOS transistor. The source of the first PMOS transistor is connected with a sub word line inverted signal obtained by inverting the sub word line signal, and the source of the first NMOS transistor is connected with a first negative voltage. A single main word line signal is connected to a gate of the first PMOS transistor and a gate of the first NMOS transistor, and the sub word line signal is connected with a gate of the second NMOS transistor.Type: GrantFiled: October 26, 2004Date of Patent: July 11, 2006Assignee: Elpida Memory, Inc.Inventors: Chiaki Dono, Yasuji Koshikawa
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Publication number: 20050117411Abstract: Disclosed is a semiconductor storage device in which the chip area is prevented from increasing to reduce the leakage current during low power (power down) time caused by shorting across bit and word lines due to crossing failure. There are provided precharge equalizing NMOS transistors the gates of which are supplied with a control signal (BLEQT). These precharge equalizing NMOS transistors are connected across a power supply line (VNLR), supplying a precharge potential to the bit line, and the bit line. At the time of low power operation, a potential (0.7 to 1.4V) lower than the potential VPP (e.g. 3.2V) applied during the precharge operation of the normal operation is supplied to the gate terminals of the transistors to reduce the leakage current caused by shorting across the bit and word lines caused in turn by crossing failure.Type: ApplicationFiled: November 24, 2004Publication date: June 2, 2005Applicant: Elpida Memory, Inc.Inventors: Yasuji Koshikawa, Chiaki Dono
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Publication number: 20050111282Abstract: A semiconductor memory device includes a pair of memory sub arrays and a control signal generating circuit. The pair of memory sub arrays shares a sense amplifier, and each of the pair of memory sub arrays has a plurality of memory cells arranged in a matrix. Each of columns of the matrix is connected to a pair of bit lines, and each of rows of the matrix is connected to a word line. The control signal generating circuit sequentially outputs first and second refresh start signals within an operation time to an external refresh command in response to an internal refresh command. A first refreshing operation is carried out to first memory cells connected to a first word line of one of the memory sub arrays in response to the first refresh start signal, and a second refreshing operation is carried out to second memory cells connected to a second word line different from the first word line in the memory sub array in response to the second refresh start signal.Type: ApplicationFiled: November 24, 2004Publication date: May 26, 2005Inventors: Chiaki Dono, Yasuji Koshikawa
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Publication number: 20050088903Abstract: In a sub word driver circuit in a semiconductor memory device of a hierarchy word structure using a main word line signal and a sub word line signal, a first NMOS transistor and a first PMOS transistor are connected in series. A second NMOS transistor is connected with a node between the first PMOS transistor and the first NMOS transistor. The source of the first PMOS transistor is connected with a sub word line inverted signal obtained by inverting the sub word line signal, and the source of the first NMOS transistor is connected with a first negative voltage. A single main word line signal is connected to a gate of the first PMOS transistor and a gate of the first NMOS transistor, and the sub word line signal is connected with a gate of the second NMOS transistor.Type: ApplicationFiled: October 26, 2004Publication date: April 28, 2005Inventors: Chiaki Dono, Yasuji Koshikawa
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Publication number: 20050052928Abstract: At first, failed cells are repaired using row redundancy or column redundancy as done in the past and then, for the remaining failed cells that cannot be repaired by row or column redundancy, by increasing the number of refreshes greater than that of normal cells, it is possible to repair more failed cells.Type: ApplicationFiled: October 6, 2004Publication date: March 10, 2005Inventor: Yasuji Koshikawa
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Patent number: 6847563Abstract: A semiconductor storage device and a method for correcting defects of memory cells, in which the semiconductor storage device has a memory cell array provided with a normal memory cell area and a redundant memory cell area. A test is conducted in the semiconductor storage device to check whether or not a defect of a memory cell exists in the normal memory cell area and/or redundant memory cell area and in which defective memory cell columns or defective memory cell rows in the normal memory cell area are replaced with redundant memory cell columns or redundant memory cell rows. In the semiconductor storage, in the test conducted on the redundant memory cell area, if redundant memory cell columns or redundant memory cell rows have already been replaced, judgment is made to exclude the redundant memory cell columns or redundant memory cell rows from the columns or rows respectively to be replaced.Type: GrantFiled: December 3, 2002Date of Patent: January 25, 2005Assignee: Elpida Memory, Inc.Inventor: Yasuji Koshikawa
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Patent number: 6636448Abstract: A semiconductor memory device (10) having a normal mode of operation and a test mode of operation is provided. The semiconductor memory device (10) can include a plurality of banks (100A to 100D). A bank (100A) may have a plurality of plates (PLT). In the normal mode of operation a row of plates (11020, 11021, . . . 11027) may be activated. In the test mode of operation, half of the row of plates (11020, 11021, . . . 11027) may be activated.Type: GrantFiled: May 29, 2001Date of Patent: October 21, 2003Assignees: NEC Corporation, NEC Electronics CorporationInventor: Yasuji Koshikawa
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Publication number: 20030103394Abstract: A semiconductor storage device and a method for remedying defects of memory cells are provided which are capable of remedying defective memory cells in an optimum manner without being affected by changes in occurrence of the defective memory cells and improving efficiency of using the redundant memory cells and increasing yields in manufacturing of the semiconductor storage device products. The semiconductor storage device has a memory cell array being provided with a normal memory cell area and a redundant memory cell area in which a test is conducted to check whether or not defect of the memory cell exist in the normal memory cell area and/or redundant memory cell area and in which defective memory cell columns or defective memory cell rows in the normal memory cell area are replaced with redundant memory cell columns or redundant memory cell rows.Type: ApplicationFiled: December 3, 2002Publication date: June 5, 2003Inventor: Yasuji Koshikawa
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Patent number: 6515921Abstract: A semiconductor storage device such as a DRAM is configured to enable testing on defectiveness of memory cells by an existing memory tester, which locates defect cells to be replaced with redundancy cells by a redundancy circuit. Herein, a write circuit writes multiple-bit data to memory cells of a memory cell array under testing. Then, the multiple-bit data are read from the memory cell array by a read circuit and are compared with original one to make decisions of “pass” or “fail” on the memory cells by the memory tester. Specifically, the read circuit is configured by plural pairs of a data output circuit and a data compression circuit with respect to plural sets of prescribed data each of which consists of a prescribed number of bits corresponding to prescribed memory cells which are subjected to simultaneous replacement.Type: GrantFiled: April 23, 2002Date of Patent: February 4, 2003Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Patent number: 6483579Abstract: A clock synchronization semiconductor memory device in which the pre-charging time tRP can be accelerated by the variable delay time for write recovery. There is provided a unit for checking whether or not at least one clock cycle before the inputting of the pre-charge command is that for the write operation, and for holding the checked result. There is also provided a unit for performing switching control at the time of inputting the pre-charge command, responsive to the checked result, as to whether or not a pre-set delay time is to be introduced as from the time of inputting the pre-charge command until word line resetting.Type: GrantFiled: January 17, 2002Date of Patent: November 19, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Patent number: 6452844Abstract: A semiconductor storage device such as a DRAM is configured to enable testing on defectiveness of memory cells by an existing memory tester, which locates defect cells to be replaced with redundancy cells by a redundancy circuit. Herein, a write circuit writes multiple-bit data to memory cells of a memory cell array under testing. Then, the multiple-bit data are read from the memory cell array by a read circuit and are compared with original one to make decisions of “pass” or “fail” on the memory cells by the memory tester. Specifically, the read circuit is configured by plural pairs of a data output circuit and a data compression circuit with respect to plural sets of prescribed data each of which consists of a prescribed number of bits corresponding to prescribed memory cells which are subjected to simultaneous replacement.Type: GrantFiled: December 18, 2000Date of Patent: September 17, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Publication number: 20020122343Abstract: A semiconductor storage device such as a DRAM is configured to enable testing on defectiveness of memory cells by an existing memory tester, which locates defect cells to be replaced with redundancy cells by a redundancy circuit Herein, a write circuit writes multiple-bit data to memory cells of a memory cell array under testing Then, the multiple-bit data are read from the memory cell array by a read circuit and are compared with original one to make decisions of “pass” or “fail” on the memory cells by the memory tester Specifically, the read circuit is configured by plural pairs of a data output circuit and a data compression circuit with respect to plural sets of prescribed data each of which consists of a prescribed number of bits corresponding to prescribed memory cells which are subjected to simultaneous replacement The data compression circuit is configured by an exclusive-or circuit that compresses a certain type of the prescribed data to specific data having a specific logicalType: ApplicationFiled: April 23, 2002Publication date: September 5, 2002Inventor: Yasuji Koshikawa
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Publication number: 20020105635Abstract: A clock synchronization semiconductor memory device in which the pre-charging time tRP can be accelerated by the variable delay time for write recovery. There is provided a unit for checking whether or not at least one clock cycle before the inputting of the pre-charge command is that for the write operation, and for holding the checked result. There is also provided a unit for performing switching control at the time of inputting the pre-charge command, responsive to the checked result, as to whether or not a pre-set delay time is to be introduced as from the time of inputting the pre-charge command until word line resetting.Type: ApplicationFiled: January 17, 2002Publication date: August 8, 2002Inventor: Yasuji Koshikawa
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Patent number: 6414887Abstract: A semiconductor memory device is designed to speed up the selection of a word line.Type: GrantFiled: May 2, 2001Date of Patent: July 2, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Patent number: 6385095Abstract: A semiconductor memory device is provided in which no delay in writing of data occurs due to increases in the output load of the data input circuit, and which is also compatible with various bit configurations. The device comprises a plurality of data input circuits for inputting data from an external source, and a plurality of data write circuits for writing data input from the plurality of data input circuits to a memory cell array. The data to be stored is input from an external source by selectively using the plurality of data input circuits, and then each bit to be stored is distributed to the plurality of data write circuits according to the bit configuration of the data. Of the plurality of data input circuits, data input from a specific data input circuit is distributed to one of the plurality of data write circuits via another data input circuit.Type: GrantFiled: December 4, 2000Date of Patent: May 7, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Patent number: 6385104Abstract: The semiconductor memory device according to the present invention comprises a memory cell array having a plurality of memory cells, a plurality of bit lines, a plurality of word lines, a row decoder which selects a prescribed word line in response to a row address and a control signal, a test mode decision circuit which generates a test signal by deciding that the device is in a test mode, a control signal generating circuit which brings the control signal to the activated state and keeps it there for a prescribed duration in response to an instruction signal, wherein the control signal generating circuit has a means for setting the change of the control signal to the inactivated state in response to the occurrence of the test signal sooner than in the normal operation.Type: GrantFiled: April 20, 2001Date of Patent: May 7, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Patent number: 6353573Abstract: A clock synchronization semiconductor memory device in which the pre-charging time tRP can be accelerated by the variable delay time for write recovery. There is provided a unit for checking whether or not at least one clock cycle before the inputting of the pre-charge command is that for the write operation, and for holding the checked result. There is also provided a unit for performing switching control at the time of inputting the pre-charge command, responsive to the checked result, as to whether or not a pre-set delay time is to be introduced as from the time of inputting the pre-charge command until word line resetting.Type: GrantFiled: May 10, 2000Date of Patent: March 5, 2002Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Publication number: 20010050870Abstract: A semiconductor memory device (10) having a normal mode of operation and a test mode of operation is provided. The semiconductor memory device (10) can include a plurality of banks (100A to 100D). A bank (100A) may have a plurality of plates (PLT). In the normal mode of operation a row of plates (11020, 11021, . . . 11027) may be activated. In the test mode of operation, half of the row of plates (11020, 11021, . . . 11027) may be activated.Type: ApplicationFiled: May 29, 2001Publication date: December 13, 2001Inventor: Yasuji Koshikawa
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Patent number: 6330198Abstract: A semiconductor storage device can improve probability of relieving of defective cell. The semiconductor storage device includes a redundancy cell for relieving a defective cell when the defective cell is found during fabrication process of a memory cell, a redundancy judgment circuit making judgment whether an input address is a column address of the defective cell or not and redundancy column selection lines for making the redundancy cell active when the redundancy judgment circuit makes judgment that the input address is the column address of the defective cell. The semiconductor storage device further includes means for dividing the redundancy cell connected to one redundancy column selection line into a plurality of divided redundancy cells and assigning the column address of the defective cell to each of divided redundancy cells as relieving address.Type: GrantFiled: June 8, 2000Date of Patent: December 11, 2001Assignee: NEC CorporationInventor: Yasuji Koshikawa
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Publication number: 20010033519Abstract: The semiconductor memory device according to the present invention comprises a memory cell array having a plurality of bit lines, a plurality of word lines installed perpendicular to the plurality of bit lines, and a plurality of memory cells disposed at the intersections of the bit lines and the word lines, a row decoder which selects a prescribed word line out of the plurality of word lines in response to a row address when a control signal is in an activated state and brings all the word lines to an unselected state when the control signal is changed to an inactivated state, a test mode decision circuit which generates a test signal by deciding that the device is in a test mode, and a control signal generating circuit which brings the control signal to the activated state and keeps it there for a prescribed duration in response to an instruction signal, wherein the control signal generating circuit has a means for setting the change of the control signal to the inactivated state in response to the occurrenType: ApplicationFiled: April 20, 2001Publication date: October 25, 2001Inventor: Yasuji Koshikawa