Patents by Inventor Keiji Hosotani

Keiji Hosotani 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: 8111538
    Abstract: A semiconductor memory device includes a memory cell array having a plurality of memory cells which are set into low-resistance states/high-resistance states according to “0” data/“1” data. An allocation of the “0” data/“1” data and the low-resistance state/high-resistance state is switched when a power source is turned on.
    Type: Grant
    Filed: November 19, 2008
    Date of Patent: February 7, 2012
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Keiji Hosotani, Yoshiaki Asao, Yoshihisa Iwata
  • Publication number: 20110254114
    Abstract: A magnetoresistive effect element includes a first ferromagnetic layer formed above a substrate, a second ferromagnetic layer formed above the first ferromagnetic layer, an insulating layer interposed between the first ferromagnetic layer and the second ferromagnetic layer and formed of a metal oxide, and a first nonmagnetic metal layer interposed between the insulating layer and the second ferromagnetic layer and in contact with a surface of the insulating layer on the side of the second ferromagnetic layer, the first nonmagnetic metal layer containing the same metal element as the metal oxide.
    Type: Application
    Filed: June 29, 2011
    Publication date: October 20, 2011
    Inventors: Makoto Nagamine, Keiji Hosotani, Hisanori Aikawa, Tomomasa Ueda, Sumio Ikegawa
  • Patent number: 7932513
    Abstract: A magnetic random access memory includes a bit line running in a first direction, a first word line running in a second direction different from the first direction, and a memory element having a magnetoresistive effect element including a fixed layer having a fixed magnetization direction, a recording layer having a reversible magnetization direction, and a nonmagnetic layer formed between the fixed layer and the recording layer, the magnetization directions in the fixed layer and the recording layer being perpendicular to a film surface, and a heater layer in contact with the magnetoresistive effect element, the memory element being connected to the bit line, and formed to oppose a side surface of the first word line such that the memory element is insulated from the first word line.
    Type: Grant
    Filed: March 6, 2008
    Date of Patent: April 26, 2011
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Keiji Hosotani, Yoshiaki Asao, Toshihiko Nagase
  • Patent number: 7920412
    Abstract: A magnetic random access memory includes a first wiring, a second wiring formed above and spaced apart from the first wiring, a magnetoresistive effect element formed between the first wiring and the second wiring, formed in contact with an upper surface of the first wiring, and having a fixed layer, a recording layer, and a nonmagnetic layer formed between the fixed layer and the recording layer, a metal layer formed on the magnetoresistive effect element and integrated with the magnetoresistive effect element to form stacked layers, a first side insulating film formed on side surfaces of the metal layer, the magnetoresistive effect element, and the first wiring, a first contact formed in contact with a side surface of the first side insulating film, and a third wiring formed on the metal layer and the first contact to electrically connect the magnetoresistive effect element and the first contact.
    Type: Grant
    Filed: October 23, 2009
    Date of Patent: April 5, 2011
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Keiji Hosotani, Yoshiaki Asao, Akihiro Nitayama
  • Patent number: 7919826
    Abstract: A magnetoresistive element includes a first stacked structure formed by sequentially stacking a first fixed layer in which a magnetization direction is fixed and a first nonmagnetic layer, a second stacked structure formed on the first stacked structure by sequentially stacking a free layer in which a magnetization direction is changeable, a second nonmagnetic layer, and a second fixed layer in which a magnetization direction is fixed, and a circumferential wall formed in contact with a circumferential surface of the second stacked structure to surround the second stacked structure, and made of an insulator. A circumferential surface of the first stacked structure is substantially perpendicular. The second stacked structure has a tapered shape which narrows upward.
    Type: Grant
    Filed: April 23, 2008
    Date of Patent: April 5, 2011
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masayoshi Iwayama, Yoshiaki Asao, Takeshi Kajiyama, Keiji Hosotani
  • Patent number: 7894246
    Abstract: A magnetoresistive element includes: a magnetization free layer having a first plane and a second plane located on the opposite side from the first plane, and having a variable magnetization direction; a magnetization pinned layer provided on the first plane side of the magnetization free layer, and having a pinned magnetization direction; a first tunnel barrier layer provided between the magnetization free layer and the magnetization pinned layer; a second tunnel barrier layer provided on the second plane of the magnetization free layer; and a non-magnetic layer provided on a plane on the opposite side of the second tunnel barrier layer from the magnetization free layer. The magnetization direction of the magnetization free layer is variable by applying current between the magnetization pinned layer and the non-magnetic layer, and a resistance ratio between the first tunnel barrier layer and the second tunnel barrier layer is in a range of 1:0.25 to 1:4.
    Type: Grant
    Filed: January 15, 2008
    Date of Patent: February 22, 2011
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tomomasa Ueda, Hisanori Aikawa, Masatoshi Yoshikawa, Naoharu Shimomura, Masahiko Nakayama, Sumio Ikegawa, Keiji Hosotani, Makoto Nagamine
  • Publication number: 20100315864
    Abstract: A magnetoresistive element includes: a magnetization free layer having a first plane and a second plane located on the opposite side from the first plane, and having a variable magnetization direction; a magnetization pinned layer provided on the first plane side of the magnetization free layer, and having a pinned magnetization direction; a first tunnel barrier layer provided between the magnetization free layer and the magnetization pinned layer; a second tunnel barrier layer provided on the second plane of the magnetization free layer; and a non-magnetic layer provided on a plane on the opposite side of the second tunnel barrier layer from the magnetization free layer. The magnetization direction of the magnetization free layer is variable by applying current between the magnetization pinned layer and the non-magnetic layer, and a resistance ratio between the first tunnel barrier layer and the second tunnel barrier layer is in a range of 1:0.25 to 1:4.
    Type: Application
    Filed: August 5, 2010
    Publication date: December 16, 2010
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Tomomasa UEDA, Hisanori Aikawa, Masatoshi Yoshikawa, Naoharu Shimomura, Masahiko Nakayama, Sumio Ikegawa, Keiji Hosotani, Makoto Nagamine
  • Patent number: 7751235
    Abstract: A semiconductor memory device includes first to fourth resistance change elements sequentially arranged apart from each other in a first direction, a first electrode which connects one terminals of the first and second resistance change elements, a second electrode which connects one terminals of the third and fourth resistance change elements, a bit line which connects the other terminals of the second and third resistance change elements, first to fourth word lines respectively paired with the first to fourth resistance change elements, arranged apart from the first and second electrodes, and running in a second direction, a first current source which supplies a first electric current to a chain structure, when writing data in a selected element, and a second current source which supplies a second electric current to a selected word line which corresponds to the selected element, when writing the data in the selected element.
    Type: Grant
    Filed: December 19, 2007
    Date of Patent: July 6, 2010
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Keiji Hosotani, Yoshiaki Asao
  • Patent number: 7727778
    Abstract: A magnetoresistive element includes a stack formed by sequentially stacking a first fixed layer in which a magnetization direction is fixed, a first nonmagnetic layer, a free layer in which a magnetization direction is changeable, a second nonmagnetic layer, and a second fixed layer in which a magnetization direction is fixed, a first circumferential wall provided on the second nonmagnetic layer in contact with a circumferential surface of the second fixed layer to surround the second fixed layer, and made of an insulator, and a second circumferential wall provided on the first nonmagnetic layer in contact with a circumferential surface of the free layer to surround the free layer, and made of an insulator.
    Type: Grant
    Filed: August 28, 2008
    Date of Patent: June 1, 2010
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masayoshi Iwayama, Keiji Hosotani, Takeshi Kajiyama, Yoshiaki Asao
  • Patent number: 7706175
    Abstract: A magnetic random access memory includes a first wiring, a second wiring formed above and spaced apart from the first wiring, a magnetoresistive effect element formed between the first wiring and the second wiring, formed in contact with an upper surface of the first wiring, and having a fixed layer, a recording layer, and a nonmagnetic layer formed between the fixed layer and the recording layer, a metal layer formed on the magnetoresistive effect element and integrated with the magnetoresistive effect element to form stacked layers, a first side insulating film formed on side surfaces of the metal layer, the magnetoresistive effect element, and the first wiring, a first contact formed in contact with a side surface of the first side insulating film, and a third wiring formed on the metal layer and the first contact to electrically connect the magnetoresistive effect element and the first contact.
    Type: Grant
    Filed: August 15, 2007
    Date of Patent: April 27, 2010
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Keiji Hosotani, Yoshiaki Asao, Akihiro Nitayama
  • Publication number: 20100078763
    Abstract: A resistance-change memory includes an interlayer insulating film, a lower electrode layer, a fixed layer, a first insulating film, a recording layer, a second insulating film, a conducting layer and an interconnect. The interlayer insulating film is formed on a semiconductor substrate and has a step. The lower electrode layer is formed on the interlayer insulating film including the step. The fixed layer is formed on the lower electrode layer and has invariable magnetization. The first insulating film is formed on the fixed layer. The recording layer is formed on part of the first insulating film and has variable magnetization. The second insulating film is over the recording layer and in contact with the first insulating film. The conducting layer is formed on the second insulating film. The interconnect is connected to the conducting layer.
    Type: Application
    Filed: September 14, 2009
    Publication date: April 1, 2010
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Keiji HOSOTANI, Yoshiaki ASAO, Kuniaki SUGIURA, Masatoshi YOSHIKAWA, Sumio IKEGAWA, Shigeki TAKAHASHI, Minoru AMANO
  • Publication number: 20100053823
    Abstract: A magnetoresistive element includes a stack formed by sequentially stacking a first fixed layer in which a magnetization direction is fixed, a first nonmagnetic layer, a free layer in which a magnetization direction is changeable, a second nonmagnetic layer, and a second fixed layer in which a magnetization direction is fixed, a first circumferential wall provided on the second nonmagnetic layer in contact with a circumferential surface of the second fixed layer to surround the second fixed layer, and made of an insulator, and a second circumferential wall provided on the first nonmagnetic layer in contact with a circumferential surface of the free layer to surround the free layer, and made of an insulator.
    Type: Application
    Filed: August 28, 2008
    Publication date: March 4, 2010
    Inventors: Masayoshi Iwayama, Keiji Hosotani, Takeshi Kajiyama, Yoshiaki Asao
  • Publication number: 20100047930
    Abstract: A magnetic random access memory includes a first wiring, a second wiring formed above and spaced apart from the first wiring, a magnetoresistive effect element formed between the first wiring and the second wiring, formed in contact with an upper surface of the first wiring, and having a fixed layer, a recording layer, and a nonmagnetic layer formed between the fixed layer and the recording layer, a metal layer formed on the magnetoresistive effect element and integrated with the magnetoresistive effect element to form stacked layers, a first side insulating film formed on side surfaces of the metal layer, the magnetoresistive effect element, and the first wiring, a first contact formed in contact with a side surface of the first side insulating film, and a third wiring formed on the metal layer and the first contact to electrically connect the magnetoresistive effect element and the first contact.
    Type: Application
    Filed: October 23, 2009
    Publication date: February 25, 2010
    Inventors: Keiji HOSOTANI, Yoshiaki Asao, Akihiro Nitayama
  • Publication number: 20100020592
    Abstract: A first magnetic layer has a magnetization fixed along one direction. A first nonmagnetic layer on the first magnetic layer functions as a first tunnel barrier. A second magnetic layer on the first nonmagnetic layer has a magnetization whose direction can be reversed by spin transfer current injection. A second nonmagnetic layer on the second magnetic layer functions as a second tunnel barrier. A third magnetic layer on the second nonmagnetic layer has a magnetization whose direction can be reversed by spin transfer through current injection at a current density different from the second magnetic layer. First magnetic, first nonmagnetic layer, and second magnetic layers exhibit a first magnetoresistive effect. Second magnetic, second nonmagnetic, and third magnetic layers exhibit a second magnetoresistive effect. A magnetoresistive effect element records and reads out data of at least three levels based on a synthetic resistance from the first and second magnetoresistive effects.
    Type: Application
    Filed: July 27, 2009
    Publication date: January 28, 2010
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Keiji HOSOTANI, Masahiko NAKAYAMA
  • Publication number: 20090129141
    Abstract: A semiconductor memory device includes a memory cell array having a plurality of memory cells which are set into low-resistance states/high-resistance states according to “0” data/“1” data. An allocation of the “0” data/“1” data and the low-resistance state/high-resistance state is switched when a power source is turned on.
    Type: Application
    Filed: November 19, 2008
    Publication date: May 21, 2009
    Inventors: Keiji HOSOTANI, Yoshiaki Asao, Yoshihisa Iwata
  • Publication number: 20090091863
    Abstract: A magnetoresistive element includes a first electrode layer, a first fixed layer provided on the first electrode layer and having a fixed magnetization direction, a first intermediate layer provided on the first fixed layer and made of a metal oxide, a free layer provided on the first intermediate layer and having a variable magnetization direction, and a second electrode layer provided on the free layer. At least one of the first electrode layer and the second electrode layer contains a conductive metal oxide.
    Type: Application
    Filed: October 1, 2008
    Publication date: April 9, 2009
    Inventors: Keiji Hosotani, Yoshiaki Asao
  • Publication number: 20080265347
    Abstract: A magnetoresistive element includes a first stacked structure formed by sequentially stacking a first fixed layer in which a magnetization direction is fixed and a first nonmagnetic layer, a second stacked structure formed on the first stacked structure by sequentially stacking a free layer in which a magnetization direction is changeable, a second nonmagnetic layer, and a second fixed layer in which a magnetization direction is fixed, and a circumferential wall formed in contact with a circumferential surface of the second stacked structure to surround the second stacked structure, and made of an insulator. A circumferential surface of the first stacked structure is substantially perpendicular. The second stacked structure has a tapered shape which narrows upward.
    Type: Application
    Filed: April 23, 2008
    Publication date: October 30, 2008
    Inventors: Masayoshi Iwayama, Yoshiaki Asao, Takeshi Kajiyama, Keiji Hosotani
  • Publication number: 20080253039
    Abstract: A magnetoresistive effect element includes a first ferromagnetic layer formed above a substrate, a second ferromagnetic layer formed above the first ferromagnetic layer, an insulating layer interposed between the first ferromagnetic layer and the second ferromagnetic layer and formed of a metal oxide, and a first nonmagnetic metal layer interposed between the insulating layer and the second ferromagnetic layer and in contact with a surface of the insulating layer on the side of the second ferromagnetic layer, the first nonmagnetic metal layer containing the same metal element as the metal oxide.
    Type: Application
    Filed: April 9, 2008
    Publication date: October 16, 2008
    Inventors: Makoto NAGAMINE, Keiji HOSOTANI, Hisanori AIKAWA, Tomomasa UEDA, Sumio IKEGAWA
  • Publication number: 20080225577
    Abstract: A magnetic random access memory includes a bit line running in a first direction, a first word line running in a second direction different from the first direction, and a memory element having a magnetoresistive effect element including a fixed layer having a fixed magnetization direction, a recording layer having a reversible magnetization direction, and a nonmagnetic layer formed between the fixed layer and the recording layer, the magnetization directions in the fixed layer and the recording layer being perpendicular to a film surface, and a heater layer in contact with the magnetoresistive effect element, the memory element being connected to the bit line, and formed to oppose a side surface of the first word line such that the memory element is insulated from the first word line.
    Type: Application
    Filed: March 6, 2008
    Publication date: September 18, 2008
    Inventors: Keiji HOSOTANI, Yoshiaki Asao, Toshihiko Nagase
  • Publication number: 20080180859
    Abstract: A magnetoresistive element includes: a magnetization free layer having a first plane and a second plane located on the opposite side from the first plane, and having a variable magnetization direction; a magnetization pinned layer provided on the first plane side of the magnetization free layer, and having a pinned magnetization direction; a first tunnel barrier layer provided between the magnetization free layer and the magnetization pinned layer; a second tunnel barrier layer provided on the second plane of the magnetization free layer; and a non-magnetic layer provided on a plane on the opposite side of the second tunnel barrier layer from the magnetization free layer. The magnetization direction of the magnetization free layer is variable by applying current between the magnetization pinned layer and the non-magnetic layer, and a resistance ratio between the first tunnel barrier layer and the second tunnel barrier layer is in a range of 1:0.25 to 1:4.
    Type: Application
    Filed: January 15, 2008
    Publication date: July 31, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Tomomasa UEDA, Hisanori AIKAWA, Masatoshi YOSHIKAWA, Naoharu SHIMOMURA, Masahiko NAKAYAMA, Sumio IKEGAWA, Keiji HOSOTANI, Makoto NAGAMINE