Patents by Inventor Yoshitaka Sasago

Yoshitaka Sasago 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).

  • Patent number: 8604456
    Abstract: Provided is a nonvolatile memory device including a phase-change memory configured with cross-point memory cells in which memory elements formed of a phase-change material and selection elements formed with a diode are combined. A memory cell is configured with a memory element formed of a phase-change material and a selection element formed with a diode having a stacked structure of a first polycrystalline silicon film, a second polycrystalline silicon film, and a third polycrystalline silicon film. The memory cells are arranged at intersection points of a plurality of first metal wirings extending along a first direction with a plurality of third metal wirings extending along a second direction orthogonal to the first direction. An interlayer film is formed between adjacent selection elements and between adjacent memory elements, and voids are formed in the interlayer film provided between the adjacent memory elements.
    Type: Grant
    Filed: February 6, 2012
    Date of Patent: December 10, 2013
    Assignee: Hitachi, Ltd.
    Inventors: Masaharu Kinoshita, Yoshitaka Sasago, Norikatsu Takaura
  • Patent number: 8592789
    Abstract: In a nonvolatile semiconductor memory device, there is provided a technique which promotes microfabrication by reducing a thickness of the device as suppressing an OFF current of a polysilicon diode which is a selective element. A polysilicon layer to which an impurity is doped at low concentration and which becomes an electric-field relaxation layer of the polysilicon diode which is a selective element of a resistance variable memory is formed so as to be divided into two or more layers such as polysilicon layers. In this manner, it is suppressed to form the crystal grain boundaries thoroughly penetrating between an n-type polysilicon layer and a p-type polysilicon layer in the electric-field relaxation layer, and therefore, it is prevented to generate a leakage current flowing through the crystal grain boundaries in application of a reverse-bias voltage without increasing a height of the polysilicon diode.
    Type: Grant
    Filed: May 17, 2011
    Date of Patent: November 26, 2013
    Assignee: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Masaharu Kinoshita, Mitsuharu Tai, Takashi Kobayashi
  • Publication number: 20130292630
    Abstract: The technical problem to be solved is to achieve high density with simple manufacturing process to decrease bit costs of memory. A semiconductor memory device according to a first aspect of the present invention includes a variable resistance material layer and a channel layer that are connected in series between a first diffusion layer and a metal wire, thereby separating the metal wire and a channel semiconductor layer. A semiconductor memory device according to a second aspect of the present invention includes a variable resistance material layer electrically connecting channel semiconductor layers opposed to each other in a first direction and electrically connecting channel semiconductor layers adjacent to each other in a second direction, wherein a plurality of the channel semiconductor layers is disposed in the second direction.
    Type: Application
    Filed: March 13, 2013
    Publication date: November 7, 2013
    Applicant: HITACHI, LTD.
    Inventors: Yoshitaka Sasago, Akira Kotabe
  • Patent number: 8563961
    Abstract: Disclosed are a semiconductor storage device and a method for manufacturing the semiconductor storage device, whereby the bit cost of memory using a variable resistance material is reduced.
    Type: Grant
    Filed: December 13, 2010
    Date of Patent: October 22, 2013
    Assignee: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Akio Shima, Satoru Hanzawa, Takashi Kobayashi, Masaharu Kinoshita, Norikastsu Takaura
  • Publication number: 20130234101
    Abstract: A vertical chain memory includes two-layer select transistors having first select transistors which are vertical transistors arranged in a matrix, and second select transistors which are vertical transistors formed on the respective first select transistors, and a plurality of memory cells connected in series on the two-layer select transistors. With this configuration, the adjacent select transistors are prevented from being selected by respective shared gates, the plurality of two-layer select transistors can be selected, independently, and a storage capacity of a non-volatile storage device is prevented from being reduced.
    Type: Application
    Filed: November 22, 2010
    Publication date: September 12, 2013
    Inventors: Yoshitaka Sasago, Masaharu Kinoshita, Takahiro Morikawa, Akio Shima, Takashi Kobayashi
  • Publication number: 20130228739
    Abstract: When a thin channel semiconductor layer formed on a side wall of a stacked film in which insulating films and gate electrodes are alternately stacked together is removed on the stacked film, a contact resistance between a vertical transistor including the channel semiconductor layer and the gate electrode, and a bit line formed on the stacked film is prevented from rising. As its means, a conductive layer electrically connected to the channel semiconductor layer is disposed immediately above the stacked film.
    Type: Application
    Filed: December 6, 2010
    Publication date: September 5, 2013
    Inventors: Yoshitaka Sasago, Masaharu Kinoshita, Mitsuharu Tai, Akio Shima, Kenzo Kurotsuchi, Takashi Kobayashi
  • Publication number: 20130141968
    Abstract: The purpose of the present invention is to improve a rewriting transmission rate and reliability of a phase change memory. To attain the purpose, a plurality of phase change memory cells (SMC or USMC) which are provided in series between a word line (2) and a bit line (3) and have a selection element and a storage element that are parallel connected with each other are entirely set, and after that, a part of the cells corresponding to a data pattern is reset. Alternatively, the reverse of the operation is carried out.
    Type: Application
    Filed: August 26, 2011
    Publication date: June 6, 2013
    Inventors: Yoshitaka Sasago, Hiroyuki Minemura, Takashi Kobayashi, Toshimichi Shintani, Satoru Hanzawa, Masaharu Kinoshita
  • Patent number: 8427865
    Abstract: There is provided a semiconductor storage device which is capable of further reducing a size of a memory cell, and increasing a storage capacity. Plural memory cells each including a transistor formed on a semiconductor substrate, and a variable resistive device having a resistance value changed by voltage supply and connected between source and drain terminals of the transistor are arranged longitudinally and in an array to configure a three-dimensional memory cell array. A memory cell structure has a double channel structure in which an inside of a switching transistor is filled with a variable resistance element, particularly, a phase change material. The switching transistor is turned off by application of a voltage to increase a channel resistance so that a current flows in the internal phase change material to operate the memory.
    Type: Grant
    Filed: April 5, 2012
    Date of Patent: April 23, 2013
    Assignee: Hitachi, Ltd.
    Inventors: Akio Shima, Yoshitaka Sasago, Masaharu Kinoshita, Toshiyuki Mine, Norikatsu Takaura, Takahiro Morikawa, Kenzo Kurotsuchi, Satoru Hanzawa
  • Publication number: 20130075684
    Abstract: A non-volatile memory device includes: a first line extending along a main surface of a substrate; a stack provided above the first line; a second line formed above the stack; a select element provided where the first and second lines intersect, the select element adapted to pass current in a direction perpendicular to the main surface; a second insulator film provided along a side surface of the stack; a channel layer provided along the second insulator film; an adhesion layer provided along the channel layer; and a variable resistance material layer provided along the adhesion layer, wherein the first and second lines are electrically connected via the select element and channel layer, a contact resistance via the adhesion layer between the channel layer and variable resistance material layer is low, and a resistance of the adhesion layer is high with respect to an extending direction of the channel layer.
    Type: Application
    Filed: August 17, 2012
    Publication date: March 28, 2013
    Inventors: Masaharu Kinoshita, Yoshitaka Sasago, Takashi Kobayashi, Hiroyuki Minemura
  • Publication number: 20120248399
    Abstract: Disclosed are a semiconductor storage device and a method for manufacturing the semiconductor storage device, whereby the bit cost of memory using a variable resistance material is reduced.
    Type: Application
    Filed: December 13, 2010
    Publication date: October 4, 2012
    Inventors: Yoshitaka Sasago, Akio Shima, Satoru Hanzawa, Takashi Kobayashi, Masaharu Kinoshita, Norikastsu Takaura
  • Publication number: 20120211717
    Abstract: A semiconductor memory device in which the cell area can be decreased and the minimum feature size is not restricted by the thickness of the material forming the memory cell. In a semiconductor memory device, a gate insulating film, a channel extending in a direction X, and a resistance change element extending in the direction X are formed successively above multiple word lines extending in a direction Y, and a portion of the channel and a portion of the resistance change element are disposed above each of the plurality of the word lines. Such configuration can decrease the cell area and ensure the degree of design freedom.
    Type: Application
    Filed: January 13, 2012
    Publication date: August 23, 2012
    Inventors: Masaharu KINOSHITA, Yoshitaka SASAGO, Takashi KOBAYASHI
  • Publication number: 20120211718
    Abstract: There is provided a semiconductor storage device which is capable of further reducing a size of a memory cell, and increasing a storage capacity. Plural memory cells each including a transistor formed on a semiconductor substrate, and a variable resistive device having a resistance value changed by voltage supply and connected between source and drain terminals of the transistor are arranged longitudinally and in an array to configure a three-dimensional memory cell array. A memory cell structure has a double channel structure in which an inside of a switching transistor is filled with a variable resistance element, particularly, a phase change material. The switching transistor is turned off by application of a voltage to increase a channel resistance so that a current flows in the internal phase change material to operate the memory.
    Type: Application
    Filed: April 5, 2012
    Publication date: August 23, 2012
    Inventors: AKIO SHIMA, Yoshitaka Sasago, Masaharu Kinoshita, Toshiyuki Mine, Norikatsu Takaura, Takahiro Morikawa, Kenzo Kurotsuchi, Satoru Hanzawa
  • Publication number: 20120132879
    Abstract: Provided is a nonvolatile memory device including a phase-change memory configured with cross-point memory cells in which memory elements formed of a phase-change material and selection elements formed with a diode are combined. A memory cell is configured with a memory element formed of a phase-change material and a selection element formed with a diode having a stacked structure of a first polycrystalline silicon film, a second polycrystalline silicon film, and a third polycrystalline silicon film. The memory cells are arranged at intersection points of a plurality of first metal wirings extending along a first direction with a plurality of third metal wirings extending along a second direction orthogonal to the first direction. An interlayer film is formed between adjacent selection elements and between adjacent memory elements, and voids are formed in the interlayer film provided between the adjacent memory elements.
    Type: Application
    Filed: February 6, 2012
    Publication date: May 31, 2012
    Inventors: MASAHARU KINOSHITA, Yoshitaka Sasago, Norikatsu Takaura
  • Patent number: 8169819
    Abstract: There is provided a semiconductor storage device which is capable of further reducing a size of a memory cell, and increasing a storage capacity. Plural memory cells each including a transistor formed on a semiconductor substrate, and a variable resistive device having a resistance value changed by voltage supply and connected between source and drain terminals of the transistor are arranged longitudinally and in an array to configure a three-dimensional memory cell array. A memory cell structure has a double channel structure in which an inside of a switching transistor is filled with a variable resistance element, particularly, a phase change material. The switching transistor is turned off by application of a voltage to increase a channel resistance so that a current flows in the internal phase change material to operate the memory.
    Type: Grant
    Filed: January 17, 2010
    Date of Patent: May 1, 2012
    Assignee: Hitachi, Ltd.
    Inventors: Akio Shima, Yoshitaka Sasago, Masaharu Kinoshita, Toshiyuki Mine, Norikatsu Takaura, Takahiro Morikawa, Kenzo Kurotsuchi, Satoru Hanzawa
  • Publication number: 20120087178
    Abstract: Adverse effects of a parasitic resistance and a parasitic capacitance of a driver circuit to a memory cell causes problems of thermal disturbance to a not-selected cell, unevenness of application voltage, degradation of a memory element in reading. A capacitor (C) is provided above or beneath a memory cell (MC) that includes a memory element to which a current write memory information and a selection element connected to the memory element. A charge stored in this capacitor writes to the memory element.
    Type: Application
    Filed: October 11, 2011
    Publication date: April 12, 2012
    Inventors: Takao WATANABE, Satoru Hanzawa, Yoshitaka Sasago
  • Publication number: 20120074368
    Abstract: A semiconductor memory device having a diode and a transistor connected in series, which prevents carriers from going from the diode into the transistor, thereby reducing the possibility of transistor deterioration. A structure to annihilate carriers from the diode is provided between a channel layer of the transistor and a diode semiconductor layer of the diode where the carriers are generated.
    Type: Application
    Filed: July 13, 2011
    Publication date: March 29, 2012
    Inventors: Yoshitaka SASAGO, Masaharu KINOSHITA, Mitsuharu TAI, Akio SHIMA, Takashi KOBAYASHI
  • Patent number: 8129705
    Abstract: Provided is a nonvolatile memory device including a phase-change memory configured with cross-point memory cells in which memory elements formed of a phase-change material and selection elements formed with a diode are combined. A memory cell is configured with a memory element formed of a phase-change material and a selection element formed with a diode having a stacked structure of a first polycrystalline silicon film, a second polycrystalline silicon film, and a third polycrystalline silicon film. The memory cells are arranged at intersection points of a plurality of first metal wirings extending along a first direction with a plurality of third metal wirings extending along a second direction orthogonal to the first direction. An interlayer film is formed between adjacent selection elements and between adjacent memory elements, and voids are formed in the interlayer film provided between the adjacent memory elements.
    Type: Grant
    Filed: May 2, 2009
    Date of Patent: March 6, 2012
    Assignee: Hitachi, Ltd.
    Inventors: Masaharu Kinoshita, Yoshitaka Sasago, Norikatsu Takaura
  • Patent number: 8132063
    Abstract: To realize a fast and highly reliable phase-change memory system of low power consumption, a semiconductor device includes: a memory device which includes a first memory array having a first area including a plurality of first memory cells and a second area including a plurality of second memory cells; a controller coupled to the memory device to issue a command to the memory device; and a condition table for storing a plurality of trial writing conditions. The controller performs trial writing in the plurality of second memory cells a plurality of times based on the plurality of trial writing conditions stored in the condition table, and determines writing conditions in the plurality of first memory cells based on a result of the trial writing. The memory device performs writing in the plurality of first memory cells based on the writing conditions instructed from the controller.
    Type: Grant
    Filed: July 26, 2011
    Date of Patent: March 6, 2012
    Assignee: Hitachi, Ltd.
    Inventors: Motoyasu Terao, Satoru Hanzawa, Hitoshi Kume, Minoru Ogushi, Yoshitaka Sasago, Masaharu Kinoshita, Norikatsu Takaura
  • Publication number: 20110284817
    Abstract: In a nonvolatile semiconductor memory device, there is provided a technique which promotes microfabrication by reducing a thickness of the device as suppressing an OFF current of a polysilicon diode which is a selective element. A polysilicon layer to which an impurity is doped at low concentration and which becomes an electric-field relaxation layer of the polysilicon diode which is a selective element of a resistance variable memory is formed so as to be divided into two or more layers such as polysilicon layers. In this manner, it is suppressed to form the crystal grain boundaries thoroughly penetrating between an n-type polysilicon layer and a p-type polysilicon layer in the electric-field relaxation layer, and therefore, it is prevented to generate a leakage current flowing through the crystal grain boundaries in application of a reverse-bias voltage without increasing a height of the polysilicon diode.
    Type: Application
    Filed: May 17, 2011
    Publication date: November 24, 2011
    Inventors: Yoshitaka SASAGO, Masaharu Kinoshita, Mitsuharu Tai, Takashi Kobayashi
  • Publication number: 20110283039
    Abstract: To realize a fast and highly reliable phase-change memory system of low power consumption, a semiconductor device includes: a memory device which includes a first memory array having a first area including a plurality of first memory cells and a second area including a plurality of second memory cells; a controller coupled to the memory device to issue a command to the memory device; and a condition table for storing a plurality of trial writing conditions. The controller performs trial writing in the plurality of second memory cells a plurality of times based on the plurality of trial writing conditions stored in the condition table, and determines writing conditions in the plurality of first memory cells based on a result of the trial writing. The memory device performs writing in the plurality of first memory cells based on the writing conditions instructed from the controller.
    Type: Application
    Filed: July 26, 2011
    Publication date: November 17, 2011
    Inventors: MOTOYASU TERAO, Satoru Hanzawa, Hitoshi Kume, Minoru Ogushi, Yoshitaka Sasago, Masaharu Kinoshita, Norikatsu Takaura