Patents by Inventor Kohei Sasaki

Kohei Sasaki 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).

  • Publication number: 20190148563
    Abstract: A trench MOS-type Schottky diode includes a first semiconductor layer including a Ga2O3-based single crystal, a second semiconductor layer that is a layer laminated on the first semiconductor layer and that includes a Ga2O3-based single crystal and a trench opened on a surface thereof opposite to the first semiconductor layer, an anode electrode formed on the surface of the second semiconductor layer opposite to the first semiconductor layer, a cathode electrode formed on a surface of the first semiconductor layer opposite to the second semiconductor layer, an insulating film covering the inner surface of the trench of the second semiconductor layer, and a trench MOS gate that is embedded in the trench of the second semiconductor layer so as to be covered with the insulating film and is in contact with the anode electrode.
    Type: Application
    Filed: April 20, 2017
    Publication date: May 16, 2019
    Applicants: TAMURA CORPORATION, National Institute of Information and Communications Technology
    Inventors: Kohei SASAKI, Masataka HIGASHIWAKI
  • Patent number: 10249767
    Abstract: A Ga2O3-based semiconductor element includes an undoped ?-Ga2O3 single crystal film disposed on a surface of a ?-Ga2O3 substrate, a source electrode and a drain electrode disposed on a same side of the undoped ?-Ga2O3 single crystal film, a gate electrode disposed on the undoped ?-Ga2O3 single crystal film between the source electrode and the drain electrode, and a region formed in the undoped ?-Ga2O3 single crystal film under the source electrode and the drain electrode and including a controlled dopant concentration.
    Type: Grant
    Filed: June 15, 2016
    Date of Patent: April 2, 2019
    Assignees: TAMURA CORPORATION, NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATION TECHNOLOGY
    Inventors: Kohei Sasaki, Masataka Higashiwaki
  • Patent number: 10230007
    Abstract: A semiconductor element includes a base substrate that includes a Ga2O3-based crystal having a thickness of not less than 0.05 ?m and not more than 50 ?m, and an epitaxial layer that includes a Ga2O3-based crystal and is epitaxially grown on the base substrate. A semiconductor element includes an epitaxial layer that includes a Ga2O3-based crystal including an n-type dopant, an ion implanted layer that is formed on a surface of the epitaxial layer and includes a higher concentration of n-type dopant than the epitaxial layer, an anode electrode connected to the epitaxial layer, and a cathode electrode connected to the ion implanted layer.
    Type: Grant
    Filed: July 24, 2015
    Date of Patent: March 12, 2019
    Assignees: TAMURA CORPORATION, NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY
    Inventors: Kohei Sasaki, Akito Kuramata, Masataka Higashiwaki
  • Publication number: 20190062942
    Abstract: Provided are a Ga2O3-based single crystal substrate including a Ga2O3-based single crystal which has a high resistance while preventing a lowering of crystal quality and a production method therefor. According to one embodiment of the present invention, the production method includes growing the Ga2O3-based single crystal while adding a Fe to a Ga2O3-based raw material, the Ga2O3-based single crystal (5) including the Fe at a concentration higher than that of a donor impurity mixed in the Ga2O3-based raw material, and cutting out the Ga2O3-based single crystal substrate from the Ga2O3-based single crystal (5).
    Type: Application
    Filed: October 26, 2018
    Publication date: February 28, 2019
    Applicant: TAMURA CORPORATION
    Inventor: Kohei SASAKI
  • Patent number: 10199512
    Abstract: A high withstand voltage Schottky barrier diode includes a first layer that includes a first Ga2O3-based single crystal including a first Group IV element and Cl at a concentration of not more than 5×1016 cm?3 and that has an effective donor concentration of not less than 1×1013 and not more than 6.0×1017 cm?3, a second layer that includes a second Ga2O3-based single crystal including a second Group IV element and that has a higher effective donor concentration than the first layer and is laminated on the first layer, an anode electrode formed on the first layer, and a cathode electrode formed on the second layer.
    Type: Grant
    Filed: March 9, 2016
    Date of Patent: February 5, 2019
    Assignees: TAMURA CORPORATION, NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY, NATIONAL UNIVERSITY CORPORATION TOKYO UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
    Inventors: Kohei Sasaki, Ken Goto, Masataka Higashiwaki, Akinori Koukitu, Yoshinao Kumagai, Hisashi Murakami
  • Patent number: 10161058
    Abstract: Provided are a Ga2O3-based single crystal substrate including a Ga2O3-based single crystal which has a high resistance while preventing a lowering of crystal quality and a production method therefor. According to one embodiment of the present invention, the production method includes growing the Ga2O3-based single crystal while adding a Fe to a Ga2O3-based raw material, the Ga2O3-based single crystal (5) including the Fe at a concentration higher than that of a donor impurity mixed in the Ga2O3-based raw material, and cutting out the Ga2O3-based single crystal substrate from the Ga2O3-based single crystal (5).
    Type: Grant
    Filed: February 26, 2014
    Date of Patent: December 25, 2018
    Assignee: Tamura Corporation
    Inventor: Kohei Sasaki
  • Publication number: 20180350967
    Abstract: A semiconductor element includes a Molecular Beam Epitaxy (MBE)-grown channel layer including a ?-Ga2O3 single crystal layer. The MBE-grown channel layer is formed on a ?-Ga2O3 single crystal substrate.
    Type: Application
    Filed: July 23, 2018
    Publication date: December 6, 2018
    Inventors: Kohei SASAKI, Masataka Higashiwaki
  • Publication number: 20180254355
    Abstract: A high withstand voltage Schottky barrier diode includes a first layer that includes a first Ga2O3-based single crystal including a first Group IV element and Cl at a concentration of not more than 5×1016 cm?3 and that has an effective donor concentration of not less than 1×1013 and not more than 6.0×1017 cm?3, a second layer that includes a second Ga2O3-based single crystal including a second Group IV element and that has a higher effective donor concentration than the first layer and is laminated on the first layer, an anode electrode formed on the first layer, and a cathode electrode formed on the second layer.
    Type: Application
    Filed: March 9, 2016
    Publication date: September 6, 2018
    Applicants: TAMURA CORPORATION, National Institute of Information and Communications Technology, National University Corporation Tokyo University of Agriculture and Technology
    Inventors: Kohei SASAKI, Ken GOTO, Masataka HIGASHIWAKI, Akinori KOUKITU, Yoshinao KUMAGAI, Hisashi MURAKAMI
  • Publication number: 20170350037
    Abstract: A method of growing a conductive Ga2O3-based crystal film by MBE includes producing a Ga vapor and a Si-containing vapor and supplying the vapors as molecular beams onto a surface of a Ga2O3-based crystal substrate so as to grow the Ga2O3-based crystal film. The Ga2O3-based crystal film includes a Si-containing Ga2O3-based single crystal film. The Si-containing vapor is produced by heating Si or a Si compound and Ga while allowing the Si or a Si compound to contact with the Ga.
    Type: Application
    Filed: June 2, 2017
    Publication date: December 7, 2017
    Applicants: TAMURA CORPORATION, Novel Crystal Techonology, Inc.
    Inventors: Kohei SASAKI, Daiki WAKIMOTO
  • Publication number: 20170288061
    Abstract: A semiconductor element includes a high-resistivity substrate that includes a ?-Ga2O3-based single crystal including an acceptor impurity, an undoped ?-Ga2O3-based single crystal layer formed on the high-resistivity substrate, and an n-type channel layer that includes a side surface surrounded by the undoped ?-Ga2O3-based single crystal layer. The undoped ?-Ga2O3-based single crystal layer includes an element isolation region.
    Type: Application
    Filed: August 6, 2015
    Publication date: October 5, 2017
    Inventors: Kohei SASAKI, Masataka HIGASHIWAKI, Man Hoi WONG
  • Publication number: 20170278933
    Abstract: A semiconductor element includes a high-resistivity substrate that includes a ?-Ga2O3-based single crystal including an acceptor impurity, a buffer layer on the high-resistivity substrate, the buffer layer including a ?-Ga2O3-based single crystal, and a channel layer on the buffer layer, the channel layer including a ?-Ga2O3-based single crystal including a donor impurity. A crystalline laminate structure includes a high-resistivity substrate that includes a ?-Ga2O3-based single crystal including an acceptor impurity, a buffer layer on the high-resistivity substrate, the buffer layer including a ?-Ga2O3-based single crystal, and a donor impurity-containing layer on the buffer layer, the donor impurity-containing layer including a ?-Ga2O3-based single crystal including a donor impurity.
    Type: Application
    Filed: August 18, 2015
    Publication date: September 28, 2017
    Inventors: Kohei SASAKI, Ken GOTO, Masataka HIGASHIWAKI, Man Hoi WONG, Akinori KOUKITO, Yoshinao KUMAGAI, Hisashi MURAKAMI
  • Publication number: 20170233892
    Abstract: Provided is a Ga2O3-based single crystal substrate capable of achieving a high processing yield. A Ga2O3-based single crystal substrate having a crack density of less than 0.05 cracks/cm can be obtained that has as a principal surface thereof a surface rotated 10-150° from the (100) plane, when a rotation direction from the (100) plane to the (001) plane via the (101) plane is defined as positive, having the [010] axis as the rotation axis.
    Type: Application
    Filed: August 6, 2015
    Publication date: August 17, 2017
    Applicant: TAMURA CORPORATION
    Inventor: Kohei SASAKI
  • Publication number: 20170213918
    Abstract: A semiconductor element includes a base substrate that includes a Ga2O3-based crystal having a thickness of not less than 0.05 ?m and not more than 50 ?m, and an epitaxial layer that includes a Ga2O3-based crystal and is epitaxially grown on the base substrate. A semiconductor element includes an epitaxial layer that includes a Ga2O3-based crystal including an n-type dopant, an ion implanted layer that is formed on a surface of the epitaxial layer and includes a higher concentration of n-type dopant than the epitaxial layer, an anode electrode connected to the epitaxial layer, and a cathode electrode connected to the ion implanted layer.
    Type: Application
    Filed: July 24, 2015
    Publication date: July 27, 2017
    Applicants: TAMURA CORPORATION, National Institute of Information and Communications Technology
    Inventors: Kohei SASAKI, Akito KURAMATA, Masataka HIGASHIWAKI
  • Patent number: 9716004
    Abstract: A crystal laminate structure, in which crystals can be epitaxially grown on a ?-Ga2O3-based substrate with high efficiency to produce a high-quality ?-Ga2O3-based crystal film on the substrate; and a method for producing the crystal laminate structure are provided. The crystal laminate structure includes: a ?-Ga2O3-based substrate, of which the major face is a face that is rotated by 50 to 90° inclusive with respect to face; and a ?-Ga2O3-based crystal film which is formed by the epitaxial crystal growth on the major face of the ?-Ga2O3-based substrate.
    Type: Grant
    Filed: August 2, 2012
    Date of Patent: July 25, 2017
    Assignee: TAMURA CORPORATION
    Inventor: Kohei Sasaki
  • Patent number: 9685515
    Abstract: A crystal laminate structure includes an epitaxial growth substrate including a ?-Ga2O3-based single crystal and a (010) plane or a plane inclined at an angle not more than 37.5° with respect to the (010) plane as a main surface thereof and a high electrical resistance, and an epitaxial crystal formed on the main surface of the epitaxial growth substrate. The epitaxial crystal includes a Ga-containing oxide.
    Type: Grant
    Filed: September 11, 2015
    Date of Patent: June 20, 2017
    Assignee: TAMURA CORPORATION
    Inventor: Kohei Sasaki
  • Patent number: 9657410
    Abstract: A Ga2O3 crystal film is epitaxially grown on a Ga2O3 crystal substrate using an MBE method, while controlling the n-type conductivity with high accuracy. Provided is a method for producing a Ga2O3 crystal film, wherein a conductive Ga2O3 crystal film is formed by epitaxial growth using an MBE method. This method for producing a Ga2O3 crystal film comprises a step wherein a Ga2O3 single crystal film containing Sn is grown by producing a Ga vapor and an Sn vapor and supplying the Ga vapor and the Sn vapor to the surface of a Ga2O3 crystal substrate as molecular beams. The Sn vapor is produced by heating Sn oxide that is filled in a cell of an MBE apparatus.
    Type: Grant
    Filed: November 27, 2012
    Date of Patent: May 23, 2017
    Assignee: TAMURA CORPORATION
    Inventor: Kohei Sasaki
  • Patent number: 9611567
    Abstract: Provided is a method for controlling a donor concentration in a Ga2O3-based single crystal body. In addition, an ohmic contact having a low resistance is formed between a Ga2O3-based single crystal body and an electrode. A donor concentration in a Ga2O3-based single crystal body is controlled by a method which includes a step wherein Si, which serves as a donor impurity, is introduced into the Ga2O3-based single crystal body by an ion implantation method at an implantation concentration of 1×1020 cm?3 or less, so that a donor impurity implanted region is formed in the Ga2O3-based single crystal body, the donor impurity implanted region having a higher donor impurity concentration than the regions into which Si is not implanted, and a step wherein Si in the donor impurity implanted region is activated by annealing, so that a high donor concentration region is formed.
    Type: Grant
    Filed: February 25, 2014
    Date of Patent: April 4, 2017
    Assignees: TAMURA CORPORATION, NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY
    Inventors: Kohei Sasaki, Masataka Higashiwaki
  • Publication number: 20160365418
    Abstract: A Ga2O3-based semiconductor element includes a ?-Ga2O3 substrate including a first conductivity type, a first ?-Ga2O3 single crystal film formed on the ?-Ga2O3 substrate, a second ?-Ga2O3 single crystal film including a second conductivity type formed on the first ?-Ga2O3 single crystal film, a source electrode formed on the second ?-Ga2O3 single crystal film, a drain electrode formed on a surface of the ?-Ga2O3 substrate opposite to the first ?-Ga2O3 single crystal film, and a gate electrode formed via a gate insulating film in a trench formed in the second ?-Ga2O3 single crystal film.
    Type: Application
    Filed: August 29, 2016
    Publication date: December 15, 2016
    Inventors: Kohei Sasaki, Masataka Higashiwaki
  • Publication number: 20160312380
    Abstract: A Ga2O3 based crystal film forming method includes epitaxially growing a Ga2O3 based crystal film over a Ga2O3 based substrate. A growth temperature for the crystal film is not lower than 560 degrees Celsius. A VI/III ratio in an atmosphere adjacent to a growing surface when the crystal film is grown is smaller than ½, or greater than 2. A crystal laminated structure includes a Ga2O3 based substrate including a first group IV element, and a Ga2O3 based crystal film including a second group IV element, the crystal film being formed over the substrate, and having a surface roughness (RMS) of smaller than 1 nm, and a thickness of not smaller than 300 nm. A coefficient of variation of a concentration distribution of the second group IV element in a depth direction in the crystal film is not more than 20 percent.
    Type: Application
    Filed: April 22, 2016
    Publication date: October 27, 2016
    Applicant: TAMURA CORPORATION
    Inventor: Kohei SASAKI
  • Publication number: 20160300953
    Abstract: A Ga2O3-based semiconductor element includes an undoped ?-Ga2O3 single crystal film disposed on a surface of a ?-Ga2O3 substrate, a source electrode and a drain electrode disposed on a same side of the undoped ?-Ga2O3 single crystal film, a gate electrode disposed on the undoped ?-Ga2O3 single crystal film between the source electrode and the drain electrode, and a region formed in the undoped ?-Ga2O3 single crystal film under the source electrode and the drain electrode and including a controlled dopant concentration.
    Type: Application
    Filed: June 15, 2016
    Publication date: October 13, 2016
    Inventors: Kohei Sasaki, Masataka Higashiwaki