Patents by Inventor Keiji Wada

Keiji Wada 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: 9153661
    Abstract: A silicon carbide substrate includes: an n type drift layer having a first surface and a second surface opposite to each other; a p type body region provided in the first surface of the n type drift layer; and an n type emitter region provided on the p type body region and separated from the n type drift layer by the p type body region. A gate insulating film is provided on the p type body region so as to connect the n type drift layer and the n type emitter region to each other. A p type Si collector layer is directly provided on the silicon carbide substrate to face the second surface of the n type drift layer.
    Type: Grant
    Filed: September 18, 2014
    Date of Patent: October 6, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Toru Hiyoshi
  • Publication number: 20150272918
    Abstract: The present invention provides new methods of intervention for anxiety associated disorders, in particular, trauma-derived disorders such as PTSD, and therapeutic or prophylactic agents for anxiety associated disorders that can be used as foods, beverages, and dietary supplements, for example, and which contain as an active ingredient n-3 polyunsaturated fatty acids contained in krill oil or fish oil, for example. The present invention further provides methods for alleviating fear memory or methods for preventing its formation by adjusting the proportion of n-3 polyunsaturated fatty acids to n-6 polyunsaturated fatty acids as ingested.
    Type: Application
    Filed: June 16, 2015
    Publication date: October 1, 2015
    Inventors: Masayuki SEKIGUCHI, Daisuke YAMADA, Jiro TAKEO, Wakako SEKI, Keiji WADA
  • Publication number: 20150279926
    Abstract: Each of first to third impurity regions of a silicon carbide substrate has a portion located on a flat surface of a first main surface. On the flat surface, a gate insulating film connects the first and third impurity regions to each other. On the flat surface, a first main electrode is in contact with the third impurity region. A second main electrode is provided on a second main surface. A side wall insulating film covers a side wall surface of the first main surface. The side wall surface is inclined by not less than 50° and not more than 80° relative to a {000-1} plane. In this way, a leakage current is suppressed in a silicon carbide semiconductor device.
    Type: Application
    Filed: October 21, 2013
    Publication date: October 1, 2015
    Inventors: Toru Hiyoshi, Keiji Wada, Takeyoshi Masuda
  • Patent number: 9107891
    Abstract: The present invention provides new methods of intervention for anxiety associated disorders, in particular, trauma-derived disorders such as PTSD, and therapeutic or prophylactic agents for anxiety associated disorders that can be used as foods, beverages, and dietary supplements, for example, and which contain as an active ingredient n-3 polyunsaturated fatty acids contained in krill oil or fish oil, for example. The present invention further provides methods for alleviating fear memory or methods for preventing its formation by adjusting the proportion of n-3 polyunsaturated fatty acids to n-6 polyunsaturated fatty acids as ingested.
    Type: Grant
    Filed: June 29, 2012
    Date of Patent: August 18, 2015
    Assignees: NIPPON SUISAN KAISHA, LTD., NATIONAL CENTER OF NEUROLOGY AND PSYCHIATRY
    Inventors: Masayuki Sekiguchi, Daisuke Yamada, Jiro Takeo, Wakako Seki, Keiji Wada
  • Patent number: 9099553
    Abstract: A MOSFET includes: a substrate having a first trench formed therein, the first trench opening on a side of one main surface; a gate insulating film; and a gate electrode. The substrate includes an n type source region, a p type body region, an n type drift region, and a p type deep region making contact with the body region and extending to a region deeper than the first trench. The first trench is formed such that a distance between the wall surface and the deep region increases with increasing distance from the main surface of the substrate.
    Type: Grant
    Filed: December 10, 2012
    Date of Patent: August 4, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Takeyoshi Masuda, Keiji Wada, Toru Hiyoshi
  • Publication number: 20150214353
    Abstract: A silicon carbide semiconductor device includes an element region and a guard ring region. A semiconductor element is provided in the element region. The guard ring region surrounds the element region in a plan view and has a first conductivity type. The semiconductor element includes a drift region having a second conductivity type different from the first conductivity type. The guard ring region includes a linear region and a curvature region continuously connected to the linear region. A value obtained by dividing a radius of curvature of an inner circumference portion of the curvature region by a thickness of the drift region is not less than 5 and not more than 10. Accordingly, there can be provided a silicon carbide semiconductor device capable of improving a breakdown voltage while suppressing decrease of on-state current.
    Type: Application
    Filed: September 4, 2013
    Publication date: July 30, 2015
    Inventors: Shunsuke Yamada, Toru Hiyoshi, Takeyoshi Masuda, Keiji Wada
  • Publication number: 20150179765
    Abstract: An MOSFET includes a silicon carbide substrate, an active layer, a gate oxide film, and a gate electrode. The active layer includes a body region where an inversion layer is formed at a region in contact with the gate oxide film by application of voltage to the gate electrode. The body region includes a low concentration region arranged at a region where an inversion layer is formed, and containing impurities of low concentration, and a high concentration region adjacent to the low concentration region in the carrier mobile direction in the inversion layer, arranged in a region where the inversion layer is formed, and containing impurities higher in concentration than in the low concentration region.
    Type: Application
    Filed: March 10, 2015
    Publication date: June 25, 2015
    Inventors: Takeyoshi Masuda, Keiji Wada, Toru Hiyoshi
  • Patent number: 9012335
    Abstract: A silicon carbide semiconductor device having excellent electrical characteristics including channel mobility and a method for manufacturing the same are provided. The method for manufacturing a silicon carbide semiconductor device includes: an epitaxial layer forming step of preparing a semiconductor film of silicon carbide; a gate insulating film forming step of forming an oxide film on a surface of the semiconductor film; a nitrogen annealing step of performing heat treatment on the semiconductor film on which the oxide film is formed, in a nitrogen-containing atmosphere; and a post heat treatment step of performing, after the nitrogen annealing step, post heat treatment on the semiconductor film on which the oxide film is formed, in an atmosphere containing an inert gas. The heat treatment temperature in the post heat treatment step is higher than that in the nitrogen annealing step and lower than a melting point of the oxide film.
    Type: Grant
    Filed: March 4, 2011
    Date of Patent: April 21, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Toru Hiyoshi, Takeyoshi Masuda, Keiji Wada
  • Patent number: 9012922
    Abstract: A substrate is provided with a main surface having an off angle of 5° or smaller relative to a reference plane. The reference plane is a {000-1} plane in the case of hexagonal system and is a {111} plane in the case of cubic system. A silicon carbide layer is epitaxially formed on the main surface of the substrate. The silicon carbide layer is provided with a trench having first and second side walls opposite to each other. Each of the first and second side walls includes a channel region. Further, each of the first and second side walls substantially includes one of a {0-33-8} plane and a {01-1-4} plane in the case of the hexagonal system and substantially includes a {100} plane in the case of the cubic system.
    Type: Grant
    Filed: September 7, 2012
    Date of Patent: April 21, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Toru Hiyoshi, Takeyoshi Masuda, Keiji Wada
  • Patent number: 9006745
    Abstract: An MOSFET includes a silicon carbide substrate, an active layer, a gate oxide film, and a gate electrode. The active layer includes a body region where an inversion layer is formed at a region in contact with the gate oxide film by application of voltage to the gate electrode. The body region includes a low concentration region arranged at a region where an inversion layer is formed, and containing impurities of low concentration, and a high concentration region adjacent to the low concentration region in the carrier mobile direction in the inversion layer, arranged in a region where the inversion layer is formed, and containing impurities higher in concentration than in the low concentration region.
    Type: Grant
    Filed: October 25, 2011
    Date of Patent: April 14, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Takeyoshi Masuda, Keiji Wada, Toru Hiyoshi
  • Patent number: 9000447
    Abstract: A first layer has n type conductivity. A second layer is epitaxially formed on the first layer and having p type conductivity. A third layer is on the second layer and having n type conductivity. ND is defined to represent a concentration of a donor type impurity. NA is defined to represent a concentration of an acceptor type impurity. D1 is defined to represent a location in the first layer away from an interface between the first layer and the second layer in a depth direction. D1 in which 1?ND/NA?50 is satisfied is within 1 ?m therefrom. A gate trench is provided to extend through the third layer and the second layer to reach the first layer. A gate insulating film covers a side wall of the gate trench. A gate electrode is embedded in the gate trench with the gate insulating film interposed therebetween.
    Type: Grant
    Filed: September 13, 2012
    Date of Patent: April 7, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Takeyoshi Masuda, Toru Hiyoshi
  • Patent number: 8981385
    Abstract: A silicon carbide semiconductor device includes a silicon carbide substrate. The silicon carbide substrate is composed of an element region provided with a semiconductor element portion and a termination region surrounding the element region as viewed in a plan view. The semiconductor element portion includes a drift region having a first conductivity type. The termination region includes a first electric field relaxing region contacting the element region and having a second conductivity type different from the first conductivity type, and a second electric field relaxing region arranged outside the first electric field relaxing region as viewed in the plan view, having the second conductivity type, and spaced from the first electric field relaxing region. A ratio calculated by dividing a width of the first electric field relaxing region by a thickness of the drift region is not less than 0.5 and not more than 1.83.
    Type: Grant
    Filed: December 12, 2013
    Date of Patent: March 17, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Takeyoshi Masuda, Toru Hiyoshi
  • Patent number: 8969993
    Abstract: A wide gap semiconductor device includes a substrate and a Schottky electrode. The substrate formed of a wide gap semiconductor material has a main face, and includes a first-conductivity-type region and a second-conductivity-type region. The Schottky electrode is arranged adjoining the main face of the substrate. At the substrate, there is foamed a trench having a side face continuous with the main face and a bottom continuous with the side face. The Schottky electrode adjoins the first-conductivity-type region at the side face of the trench and the main face, and adjoins the second-conductivity-type region at the bottom of the trench. The side face of the trench is inclined relative to the main face of the substrate.
    Type: Grant
    Filed: July 25, 2013
    Date of Patent: March 3, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Takeyoshi Masuda, Toru Hiyoshi
  • Patent number: 8963163
    Abstract: A semiconductor device having a construction capable of achieving suppressed deterioration of electric characteristics in an insulating member is provided. An n? SiC layer, a source contact electrode formed on a main surface of the n? SiC layer, a gate electrode arranged at a distance from the source contact electrode on the main surface of the n? SiC layer, and an interlayer insulating film located between the source contact electrode and the gate electrode are provided. A rate of lowering in electric resistance in the interlayer insulating film when heating to a temperature not higher than 1200 ° C. is carried out while the source contact electrode and the interlayer insulating film are adjacent to each other is not higher than 5%.
    Type: Grant
    Filed: July 8, 2010
    Date of Patent: February 24, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Hideto Tamaso
  • Patent number: 8963234
    Abstract: The substrate is made of a compound semiconductor, and has a recess, which opens at one main surface and has side wall surfaces when viewed in a cross section along a thickness direction. The gate insulating film is disposed on and in contact with each of the side wall surfaces. The substrate includes a source region having first conductivity type and disposed to be exposed at the side wall surface; and a body region having second conductivity type and disposed in contact with the source region at a side opposite to the one main surface so as to be exposed at the side wall surface, when viewed from the source region. The recess has a closed shape when viewed in a plan view. The side wall surfaces provide an outwardly projecting shape in every direction when viewed from an arbitrary location in the recess.
    Type: Grant
    Filed: April 15, 2013
    Date of Patent: February 24, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Takeyoshi Masuda, Toru Hiyoshi, Keiji Wada
  • Patent number: 8952393
    Abstract: A first drift layer has a first surface facing a first electrode and electrically connected to a first electrode, and a second surface opposite to the first surface. The first drift layer has an impurity concentration NA. A relaxation region is provided in a portion of the second surface of the first drift layer. The first drift layer and the second drift layer form a drift region in which the relaxation region is buried. The second drift layer has an impurity concentration NB, NB>NA being satisfied. A body region, a source region, and a second electrode are provided on the second drift layer.
    Type: Grant
    Filed: February 10, 2014
    Date of Patent: February 10, 2015
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Takeyoshi Masuda, Toru Hiyoshi
  • Publication number: 20150004757
    Abstract: A silicon carbide substrate includes: an n type drift layer having a first surface and a second surface opposite to each other; a p type body region provided in the first surface of the n type drift layer; and an n type emitter region provided on the p type body region and separated from the n type drift layer by the p type body region. A gate insulating film is provided on the p type body region so as to connect the n type drift layer and the n type emitter region to each other. A p type Si collector layer is directly provided on the silicon carbide substrate to face the second surface of the n type drift layer.
    Type: Application
    Filed: September 18, 2014
    Publication date: January 1, 2015
    Inventors: Keiji Wada, Toru Hiyoshi
  • Patent number: 8921932
    Abstract: The substrate is made of a compound semiconductor and has a plurality of first recesses, each of which opens at one main surface thereof and has a first side wall surface. The gate insulating film is disposed on and in contact with the first side wall surface. The gate electrode is disposed on and in contact with the gate insulating film. The substrate include: a source region having first conductivity type and disposed to face itself with a first recess interposed therebetween, when viewed in a cross section along the thickness direction; and a body region having second conductivity type and disposed to face itself with the first recess interposed therebetween. Portions of the source region facing each other are connected to each other in a region interposed between the first recess and another first recess adjacent to the first recess, when viewed in a plan view.
    Type: Grant
    Filed: April 15, 2013
    Date of Patent: December 30, 2014
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Takeyoshi Masuda, Keiji Wada, Toru Hiyoshi
  • Patent number: 8901568
    Abstract: A termination configuration of a silicon carbide insulating gate type semiconductor device includes a semiconductor layer of a first conductivity type having a first main face, a gate electrode, and a source interconnection, as well as a circumferential resurf region. The semiconductor layer includes a body region of a second conductivity type, a source region of the first conductivity type, a contact region of the second conductivity type, and a circumferential resurf region of the second conductivity type. A width of a portion of the circumferential resurf region excluding the body region is greater than or equal to ½ the thickness of at least the semiconductor layer. A silicon carbide insulating gate type semiconductor device of high breakdown voltage and high performance can be provided.
    Type: Grant
    Filed: February 7, 2011
    Date of Patent: December 2, 2014
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Takeyoshi Masuda, Keiji Wada, Misako Honaga
  • Patent number: 8878192
    Abstract: A silicon carbide substrate includes a first layer of a first conductivity type, a second layer of a second conductivity type provided on the first layer, and a third layer provided on the second layer and doped with an impurity for providing the first conductivity type. The silicon carbide substrate has a trench formed through the third layer and the second layer to reach the first layer. The first layer has a concentration peak of the impurity in a position away from the trench in the first layer. As a result, a silicon carbide semiconductor device having an electric field relaxation structure that can be readily formed is provided.
    Type: Grant
    Filed: April 15, 2013
    Date of Patent: November 4, 2014
    Assignee: Sumitomo Electric Industries, Ltd.
    Inventors: Keiji Wada, Toru Hiyoshi, Takeyoshi Masuda