Patents by Inventor Ryotaro Azuma
Ryotaro Azuma 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: 8325508Abstract: A writing method optimum for a variable resistance element which can maximize an operation window of the variable resistance element is provided. The writing method is performed for a variable resistance element that reversibly changes between a high resistance state and a low resistance state depending on a polarity of an applied voltage pulse. The writing method includes a preparation step (S50) and a writing step (S51, S51a, S51b). At the preparation step (S50), resistance values of the variable resistance element are measured by applying voltage pulses of voltages that are gradually increased to the variable resistance element, thereby determining the first voltage V1 for starting high resistance writing and the second voltage V2 having a maximum resistance value.Type: GrantFiled: June 8, 2010Date of Patent: December 4, 2012Assignee: Panasonic CorporationInventors: Ken Kawai, Kazuhiko Shimakawa, Shunsaku Muraoka, Ryotaro Azuma
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Patent number: 8320159Abstract: Each of memory cells (MC) includes one transistor and one resistance variable element. The transistor includes a first main terminal, a second main terminal and a control terminal. The resistance variable element includes a first electrode, a second electrode and a resistance variable layer provided between the first electrode and the second electrode. A first main terminal of one of two adjacent memory cells is connected to a second main terminal of the other memory cell, to form a series path (SP) sequentially connecting main terminals of the plurality of memory cells in series.Type: GrantFiled: March 15, 2010Date of Patent: November 27, 2012Assignee: Panasonic CorporationInventors: Zhiqiang Wei, Ryotaro Azuma, Takeshi Takagi, Mitsuteru Iijima, Yoshihiko Kanzawa
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Patent number: 8305795Abstract: To provide a variable resistance element writing method that, even when a variable resistance element has a possibility of becoming a half LR state, can ensure a maximum resistance change window by correcting the variable resistance element to a normal low resistance state.Type: GrantFiled: April 27, 2010Date of Patent: November 6, 2012Assignee: Panasonic CorporationInventors: Ryotaro Azuma, Kazuhiko Shimakawa, Shunsaku Muraoka, Ken Kawai
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Publication number: 20120236628Abstract: In a nonvolatile memory device, basic array planes (0 to 3) have respective first via groups (121 to 124) that interconnect only even-layer bit lines in the basic array planes, and respective second via groups (131 to 134) that interconnect only odd-layer bit lines in the basic array planes, the first via group in a first basic array plane and the second via group in a second basic array plane adjacent to the first basic array plane in a Y direction are adjacent to each other in the Y direction, and the first via group in the second basic array plane is connected to an unselected-bit-line dedicated global bit line (GBL_NS) having a fixed potential when the first via group in the first basic array plane is connected to a first global bit line related to the first basic array plane.Type: ApplicationFiled: November 24, 2011Publication date: September 20, 2012Inventors: Yuichiro Ikeda, Kazuhiko Shimakawa, Ryotaro Azuma
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Publication number: 20120176834Abstract: Each of basic array planes has a first via group that interconnects only even-layer bit lines in the basic array plane, and a second via group that interconnects only odd-layer bit lines in the basic array plane, the first via group in a first basic array plane and the second via group in a second basic array plane adjacent to the first basic array in a Y direction are adjacent to each other in the Y direction, and the second via group in the first basic array plane and the first via group in the second basic array plane are adjacent to each other in the Y direction, and the second via group in the second basic array plane is disconnected from a second global line when connecting the first via group in the first basic array plane to a first global line.Type: ApplicationFiled: August 10, 2011Publication date: July 12, 2012Inventors: Yuichiro Ikeda, Kazuhiko Shimakawa, Ryotaro Azuma
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Patent number: 8198618Abstract: A nonvolatile memory device of the present invention comprises a substrate (1), first wires (3), first filling constituents (5) filled into first through-holes (4), respectively, second wires (11) which cross the first wires (3) perpendicularly to the first wires (3), respectively, each of the second wires (11) including a plurality of layers including a resistance variable layer (6) of each of first resistance variable elements, a conductive layer (7) and a resistance variable layer (8) of each of second resistance variable elements which are stacked together in this order, second filling constituents (14) filled into second through-holes (13), respectively, and third wires (15), and the conductive layer (7) of the second wires (11) serves as the electrodes of the first resistance variable elements (9) and the electrodes of the second resistance variable elements (10).Type: GrantFiled: December 2, 2008Date of Patent: June 12, 2012Assignee: Panasonic CorporationInventors: Takumi Mikawa, Kenji Tominaga, Kazuhiko Shimakawa, Ryotaro Azuma
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Publication number: 20120120712Abstract: An optimum forming method of performing a forming for a variable resistance element to maximize an operation window of the variable resistance element is provided. The forming method is used to initialize a variable resistance element (100). The forming method includes: a determination step (S35) of determining whether or not a current resistance value of the variable resistance element (100) is lower than a resistance value in a high resistance state; and a voltage application step (S36) of applying a voltage pulse having a voltage not exceeding a sum of a forming voltage and a forming margin when the determination is made that the current resistance value is not lower than the resistance value in the high resistance state (No at S35). The determination step (S35) and the voltage application step (S36) are repeated to process all memory cells in a memory array (202) (S34 to S37).Type: ApplicationFiled: June 4, 2010Publication date: May 17, 2012Inventors: Ken Kawai, Kazuhiko Shimakawa, Shunsaku Muraoka, Ryotaro Azuma
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Publication number: 20120099367Abstract: A cross point variable resistance nonvolatile memory device includes memory cells having the same orientation for stable characteristics of all layers. Each memory cell (51) is placed at a different one of cross points of bit lines (53) in an X direction and word lines (52) in a Y direction formed in layers. In a multilayer cross point structure where vertical array planes sharing the word lines are aligned in the Y direction each for a group of bit lines aligned in a Z direction, even and odd layer bit line selection switch elements (57, 58) switch electrical connection and disconnection between a global bit line (56) and commonly-connected even layer bit lines and commonly-connected odd layer bit lines, respectively. A bidirectional current limiting circuit (92) having parallel-connected P-type current limiting element (91) and N-type current limiting element (90) is provided between the global bit line and the switch elements.Type: ApplicationFiled: June 2, 2011Publication date: April 26, 2012Inventors: Ryotaro Azuma, Kazuhiko Shimakawa
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Patent number: 8154909Abstract: A resistance variable memory apparatus (100) of the present invention includes a current suppressing element (116) which is connected in series with each resistance variable layer (114) and whose threshold voltage is VF, and is configured to apply a first voltage V1 to a first wire (WL) associated with a selected nonvolatile memory element, apply a second voltage V2 to a second wire (BL) associated with the selected nonvolatile memory element, apply a third voltage V3 to a first wire (WL) which is not associated with the selected nonvolatile memory element and apply a fourth voltage V4 to a second wire (BL) which is not associated with the selected memory element when writing data or reading data, wherein V2?V3<V5 and V5<V4?V1 are satisfied and (V1?V4)<VF or (V3?V2)<VF is satisfied when V5=(V1+V2)/2 is a fifth voltage V5.Type: GrantFiled: June 21, 2011Date of Patent: April 10, 2012Assignee: Panasonic CorporationInventors: Ryotaro Azuma, Kazuhiko Shimakawa, Satoru Fujii
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Patent number: 8125817Abstract: To provide a nonvolatile storage device (100) which is capable of achieving stable operation and includes variable resistance elements. The nonvolatile storage device (100) includes: memory cells (M111, M112, . . .) each of which is provided at three-dimensional cross-points between word lines (WL0, WL1, . . .) and bit lines (BL0, BL1, . . .) and having a resistance value that reversibly changes based on an electrical signal; a row selection circuit-and-driver (103) provided with transistors (103a) each of which applies a predetermined voltage to a corresponding one of the word lines (WL0, WL1, . . .); a column selection circuit-and-driver (104) provided with transistors (104a) each of which applies a predetermined voltage to a corresponding one of the bit lines (BL0, BL1, . . .); and a substrate bias circuit (110) which applies a forward bias voltage to a substrate of such transistors (103a and 104a).Type: GrantFiled: December 16, 2009Date of Patent: February 28, 2012Assignee: Panasonic CorporationInventors: Takeshi Takagi, Shunsaku Muraoka, Ryotaro Azuma, Kunitoshi Aono
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Publication number: 20110249486Abstract: A resistance variable memory apparatus (100) of the present invention includes a current suppressing element (116) which is connected in series with each resistance variable layer (114) and whose threshold voltage is VF, and is configured to apply a first voltage V1 to a first wire (WL) associated with a selected nonvolatile memory element, apply a second voltage V2 to a second wire (BL) associated with the selected nonvolatile memory element, apply a third voltage V3 to a first wire (WL) which is not associated with the selected nonvolatile memory element and apply a fourth voltage V4 to a second wire (BL) which is not associated with the selected memory element when writing data or reading data, wherein V2?V3<V5 and V5<V4?V1 are satisfied and (V1?V4)<VF or (V3?V2)<VF is satisfied when V5=(V1+V2)/2 is a fifth voltage V5.Type: ApplicationFiled: June 21, 2011Publication date: October 13, 2011Applicant: Panasonic CorporationInventors: Ryotaro AZUMA, Kazuhiko Shimakawa, Satoru Fujii
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Patent number: 7990754Abstract: A resistance variable memory apparatus (100) of the present invention includes a current suppressing element (116) which is connected in series with each resistance variable layer (114) and whose threshold voltage is VF, and is configured to apply a first voltage V1 to a first wire (WL) associated with a selected nonvolatile memory element, apply a second voltage V2 to a second wire (BL) associated with the selected nonvolatile memory element, apply a third voltage V3 to a first wire (WL) which is not associated with the selected nonvolatile memory element and apply a fourth voltage V4 to a second wire (BL) which is not associated with the selected memory element when writing data or reading data, wherein V2?V3<V5 and V5<V4?V1 are satisfied and (V1?V4)<VF or (V3?V2)<VF is satisfied when V5=(V1+V2)/2 is a fifth voltage V5.Type: GrantFiled: May 15, 2008Date of Patent: August 2, 2011Assignee: Panasonic CorporationInventors: Ryotaro Azuma, Kazuhiko Shimakawa, Satoru Fujii
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Publication number: 20110128773Abstract: To provide a variable resistance element writing method that, even when a variable resistance element has a possibility of becoming a half LR state, can ensure a maximum resistance change window by correcting the variable resistance element to a normal low resistance state.Type: ApplicationFiled: April 27, 2010Publication date: June 2, 2011Inventors: Ryotaro Azuma, Kazuhiko Shimakawa, Shunsaku Muraoka, Ken Kawai
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Publication number: 20110122680Abstract: A nonvolatile resistance variable memory device (100) includes memory cells (M11, M12, . . . ) in each of which a variable resistance element (R11, R12, . . . ) including a variable resistance layer placed between and in contact with a first electrode and a second electrode, and a current steering element (D11, D12, . . . ) including a current steering layer placed between and in contact with a third electrode and a fourth electrode, are connected in series, and the device is driven by a first LR drive circuit (105a1) via a current limit circuit (105b) to decrease resistance of the variable resistance element while the device is driven by a second HR drive circuit (105a2) to increase resistance of the variable resistance element, thus using the current limit circuit (105b) to make a current for decreasing resistance of the variable resistance element lower than a current for increasing resistance of the variable resistance element.Type: ApplicationFiled: April 14, 2010Publication date: May 26, 2011Inventors: Yuuichirou Ikeda, Kazuhiko Shimakawa, Yoshihiko Kanzawa, Shunsaku Muraoka, Ryotaro Azuma
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Publication number: 20110110144Abstract: A writing method optimum for a variable resistance element which can maximize an operation window of the variable resistance element is provided. The writing method is performed for a variable resistance element that reversibly changes between a high resistance state and a low resistance state depending on a polarity of an applied voltage pulse. The writing method includes a preparation step (S50) and a writing step (S51, S51a, S51b). At the preparation step (S50), resistance values of the variable resistance element are measured by applying voltage pulses of voltages that are gradually increased to the variable resistance element, thereby determining the first voltage V1 for starting high resistance writing and the second voltage V2 having a maximum resistance value.Type: ApplicationFiled: June 8, 2010Publication date: May 12, 2011Applicant: PANASONIC CORPORATIONInventors: Ken Kawai, Kazuhiko Shimakawa, Shunsaku Muraoka, Ryotaro Azuma
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Patent number: 7920408Abstract: Memory cells (MC) are formed at intersections of bit lines (BL) extending in the X direction and word lines (WL) extending in the Y direction. A plurality of basic array planes sharing the word lines (WL), each formed for a group of bit lines (BL) aligned in the Z direction, are arranged side by side in the Y direction. In each basic array plane, bit lines in even layers and bit lines in odd layers are individually connected in common. Each of selection switch elements (101 to 104) controls switching of electrical connection/non-connection between the common-connected even layer bit line and a global bit line (GBL), and each of selection switch elements (111 to 114) control switching of connection/non-connection between the common-connected odd layer bit line and the global bit line (GBL).Type: GrantFiled: June 20, 2008Date of Patent: April 5, 2011Assignee: Panasonic CorporationInventors: Ryotaro Azuma, Kazuhiko Shimakawa, Satoru Fujii, Yoshihiko Kanzawa
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Publication number: 20110075469Abstract: Each of memory cells (MC) includes one transistor and one resistance variable element. The transistor includes a first main terminal, a second main terminal and a control terminal. The resistance variable element includes a first electrode, a second electrode and a resistance variable layer provided between the first electrode and the second electrode. A first main terminal of one of two adjacent memory cells is connected to a second main terminal of the other memory cell, to form a series path (SP) sequentially connecting main terminals of the plurality of memory cells in series.Type: ApplicationFiled: March 15, 2010Publication date: March 31, 2011Inventors: Zhiqiang Wei, Ryotaro Azuma, Takeshi Takagi, Mitsuteru Iijima, Yoshihiko Kanzawa
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Publication number: 20100321982Abstract: To provide a nonvolatile storage device (100) which is capable of achieving stable operation and includes variable resistance elements. The nonvolatile storage device (100) includes: memory cells (M111, M112, . . . ) each of which is provided at three-dimensional cross-points between word lines (WL0, WL1, . . . ) and bit lines (BL0, BL1, . . . ) and having a resistance value that reversibly changes based on an electrical signal; a row selection circuit-and-driver (103) provided with transistors (103a) each of which applies a predetermined voltage to a corresponding one of the word lines (WL0, WL1, . . . ); a column selection circuit-and-driver (104) provided with transistors (104a) each of which applies a predetermined voltage to a corresponding one of the bit lines (BL0, BL1, . . . ); and a substrate bias circuit (110) which applies a forward bias voltage to a substrate of such transistors (103a and 104a).Type: ApplicationFiled: December 16, 2009Publication date: December 23, 2010Inventors: Takeshi Takagi, Shunsaku Muraoka, Ryotaro Azuma, Kunitoshi Aono
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Publication number: 20100264393Abstract: A nonvolatile memory device of the present invention comprises a substrate (1), first wires (3), first filling constituents (5) filled into first through-holes (4), respectively, second wires (11) which cross the first wires (3) perpendicularly to the first wires (3), respectively, each of the second wires (11) including a plurality of layers including a resistance variable layer (6) of each of first resistance variable elements, a conductive layer (7) and a resistance variable layer (8) of each of second resistance variable elements which are stacked together in this order, second filling constituents (14) filled into second through-holes (13), respectively, and third wires (15), and the conductive layer (7) of the second wires (11) serves as the electrodes of the first resistance variable elements (9) and the electrodes of the second resistance variable elements (10).Type: ApplicationFiled: December 2, 2008Publication date: October 21, 2010Inventors: Takumi Mikawa, Kenji Tominaga, Kazuhiko Shimakawa, Ryotaro Azuma
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Publication number: 20100258779Abstract: A nonvolatile memory device of the present invention includes a substrate (1), first wires (3), first resistance variable elements (5) and lower electrodes (6) of first diode elements which are filled in first through-holes (4), respectively, second wires (11) which cross the first wires 3 perpendicularly to the first wires 3, respectively, and each of which includes a semiconductor layer (7) of a first diode elements, a conductive layer (8) and a semiconductor layer (10) of a second diode elements which are stacked together in this order, second resistance variable elements (16) and upper electrodes (14) of second diode elements which are filled into second through holes (13), respectively, and third wires (17), and the conductive layer (8) of each second wires (11) also serves as the upper electrode of the first diode elements (9) and the lower electrode of the second diode elements (15).Type: ApplicationFiled: November 6, 2008Publication date: October 14, 2010Inventors: Takumi Mikawa, Kenji Tominaga, Kazuhiko Shimakawa, Ryotaro Azuma