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).
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Publication number: 20210343879Abstract: An object of the present invention is to provide a Schottky barrier diode less liable to cause dielectric breakdown due to concentration of an electric field. A Schottky barrier diode according to this disclosure includes a semiconductor substrate made of gallium oxide, a drift layer made of gallium oxide and provided on the semiconductor substrate, an anode electrode brought into Schottky contact with the drift layer, and a cathode electrode brought into ohmic contact with the semiconductor substrate. The drift layer has an outer peripheral trench surrounding the anode electrode in a plan view. The surface of the drift layer positioned between the anode electrode and the outer peripheral trench is covered with a semiconductor layer having a conductivity type opposite to that of the drift layer.Type: ApplicationFiled: October 9, 2019Publication date: November 4, 2021Inventors: Jun ARIMA, Minoru FUJITA, Jun HIRABAYASHI, Kohei SASAKI
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Publication number: 20210238766Abstract: 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: ApplicationFiled: April 21, 2021Publication date: August 5, 2021Applicant: TAMURA CORPORATIONInventor: Kohei SASAKI
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Patent number: 11081598Abstract: A trench MOS 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, a cathode electrode formed on a surface of the first semiconductor layer, an insulating film covering an inner surface of the trench, and a trench MOS gate that is buried in the trench so as to be covered with the insulating film and is in contact with the anode electrode. The second semiconductor layer includes a lower layer on a side of the first semiconductor layer and an upper layer on a side of the anode electrode having a higher donor concentration than the lower layer.Type: GrantFiled: February 27, 2018Date of Patent: August 3, 2021Assignees: TAMURA CORPORATION, NOVEL CRYSTAL TECHNOLOGY, INC.Inventors: Kohei Sasaki, Masataka Higashiwaki
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Patent number: 11043602Abstract: Provided is a Schottky barrier diode which is configured from a Ga2O3-based semiconductor, and has a lower rising voltage than a conventional one. In one embodiment, the Schottky barrier diode 1 is provided which has: a semiconductor layer 10 configured from a Ga2O3-based single crystal; an anode electrode 11 which forms a Schottky junction with the semiconductor layer 10, and has a portion which contacts the semiconductor layer 10 and is composed of Fe or Cu; and a cathode electrode 12.Type: GrantFiled: February 19, 2018Date of Patent: June 22, 2021Assignees: Tamura Corporation, Novel Crystal Technology, Inc.Inventors: Kohei Sasaki, Daiki Wakimoto, Yuki Koishikawa, Quang Tu Thieu
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Publication number: 20210167225Abstract: A Schottky barrier diode includes a semiconductor substrate made of gallium oxide, a drift layer made of gallium oxide and provided on the semiconductor substrate, an anode electrode brought into Schottky contact with the drift layer, and a cathode electrode brought into ohmic contact with the semiconductor substrate. The drift layer has a plurality of trenches formed in a position overlapping the anode electrode in a plan view. Among the plurality of trenches, a trench positioned at the end portion has a selectively increased width. Thus, the curvature radius of the bottom portion of the trench is increased, or an edge part constituted by the bottom portion as viewed in a cross section is divided into two parts. As a result, an electric field to be applied to the bottom portion of the trench positioned at the end portion is mitigated, making dielectric breakdown less likely to occur.Type: ApplicationFiled: September 26, 2018Publication date: June 3, 2021Inventors: Jun ARIMA, Jun HIRABAYASHI, Minoru FUJITA, Kohei SASAKI
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Publication number: 20210151611Abstract: A Schottky barrier diode includes a semiconductor layer including a Ga2O3-based single crystal, an anode electrode that forms a Schottky junction with the semiconductor layer and is configured so that a portion in contact with the semiconductor layer includes Mo or W, and a cathode electrode. A turn-on voltage thereof is not less than 0.3 V and not more than 0.5 V.Type: ApplicationFiled: June 12, 2018Publication date: May 20, 2021Applicants: TAMURA CORPORATION, Novel Crystal Technology, Inc.Inventors: Kohei SASAKI, Daiki WAKIMOTO, Yuki KOISHIKAWA, Quang Tu THIEU
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Patent number: 11011653Abstract: Provided is a Schottky barrier diode which is configured from a Ga2O3-based semiconductor, and has a lower rising voltage than a conventional one. In one embodiment, the Schottky barrier diode 1 is provided which has: a semiconductor layer 10 configured from a Ga2O3-based single crystal; an anode electrode 11 which forms a Schottky junction with the semiconductor layer 10, and has a portion which contacts the semiconductor layer 10 and is composed of Fe or Cu; and a cathode electrode 12.Type: GrantFiled: February 19, 2018Date of Patent: May 18, 2021Assignees: Tamura Corporation, Novel Crystal Technology, Inc.Inventors: Kohei Sasaki, Daiki Wakimoto, Yuki Koishikawa, Quang Tu Thieu
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Publication number: 20210119062Abstract: An object of the present invention is to provide a Schottky barrier diode less apt to cause dielectric breakdown due to concentration of an electric field. A Schottky barrier diode includes a semiconductor substrate 20 made of gallium oxide, a drift layer 30 made of gallium oxide and provided on the semiconductor substrate 20, an anode electrode 40 brought into Schottky contact with the drift layer 30, and a cathode electrode 50 brought into ohmic contact with the semiconductor substrate 20. The drift layer 30 has an outer peripheral trench 10 that surrounds the anode electrode 40 in a plan view, and the outer peripheral trench 10 is filled with a semiconductor material 11 having a conductivity type opposite to that of the drift layer 30. An electric field is dispersed by the presence of the thus configured outer peripheral trench 10. This alleviates electric field concentration on the corner of the anode electrode 40, making it less apt to cause dielectric breakdown.Type: ApplicationFiled: March 11, 2019Publication date: April 22, 2021Inventors: Jun ARIMA, Minoru FUJITA, Jun HIRABAYASHI, Kohei SASAKI
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Publication number: 20210020789Abstract: A trench MOS Schottky diode includes a first semiconductor layer including a Ga2O3-based single crystal, a second semiconductor layer that is a layer stacked on the first semiconductor layer, includes a Ga2O3-based single crystal, and includes 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, a cathode electrode formed on a surface of the first semiconductor layer, an insulating film covering the inner surface of the trench of the second semiconductor layer, and a trench electrode that is buried 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. The second semiconductor layer includes an insulating dry-etching-damaged layer with a thickness of not more than 0.8 ?m in a region including the inner surface of the trench.Type: ApplicationFiled: February 25, 2019Publication date: January 21, 2021Applicants: TAMURA CORPORATION, Novel Crystal Technology, Inc., TDK CorporationInventors: Kohei SASAKI, Minoru FUJITA, Jun HIRABAYASHI, Jun ARIMA
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Patent number: 10861945Abstract: 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: GrantFiled: August 18, 2015Date of Patent: December 8, 2020Assignees: TAMURA CORPORATION, NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY, NATIONAL UNIVERSITY CORPORATION TOKYO UNIVERSITY OF AGRICULTURE AND TECHNOLOGYInventors: Kohei Sasaki, Ken Goto, Masataka Higashiwaki, Man Hoi Wong, Akinori Koukitu, Yoshinao Kumagai, Hisashi Murakami
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Patent number: 10825935Abstract: 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: GrantFiled: April 20, 2017Date of Patent: November 3, 2020Assignees: TAMURA CORPORATION, National Institute of Information and Communications TechnologyInventors: Kohei Sasaki, Masataka Higashiwaki
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Publication number: 20200235234Abstract: A field-effect transistor includes an n-type semiconductor layer that includes a Ga2O3-based single crystal and a plurality of trenches opening on one surface, a gate electrode buried in each of the plurality of trenches, a source electrode connected to a mesa-shaped region between adjacent trenches in the n-type semiconductor layer, and a drain electrode directly or indirectly connected to the n-type semiconductor layer on an opposite side to the source electrode.Type: ApplicationFiled: September 26, 2018Publication date: July 23, 2020Applicants: TAMURA CORPORATION, Novel Crystal Technology, Inc.Inventor: Kohei SASAKI
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Publication number: 20200168460Abstract: A semiconductor substrate includes a single crystal Ga2O3-based substrate and a polycrystalline substrate that are bonded to each other. A thickness of the single crystal Ga2O3-based substrate is smaller than a thickness of the polycrystalline substrate, and a fracture toughness value of the polycrystalline substrate is higher than a fracture toughness value of the single crystal Ga2O3-based substrate.Type: ApplicationFiled: July 9, 2018Publication date: May 28, 2020Applicants: TAMURA CORPORATION, SICOXS Corporation, National Institute of Information and Communications TechnologyInventors: Akito KURAMATA, Shinya WATANABE, Kohei SASAKI, Kuniaki YAGI, Naoki HATTA, Masataka HIGASHIWAKI, Keita KONISHI
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Publication number: 20200168711Abstract: A diode includes an n-type semiconductor layer including an n-type Ga2O3-based single crystal, and a p-type semiconductor layer including a p-type semiconductor in which a volume of an amorphous portion is higher than a volume of a crystalline portion. The n-type semiconductor layer and the p-type semiconductor layer form a pn junction.Type: ApplicationFiled: July 23, 2018Publication date: May 28, 2020Applicants: TAMURA CORPORATION, Novel Crystal Technology, Inc.Inventor: Kohei SASAKI
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Publication number: 20200144377Abstract: A Ga2O3-based semiconductor device includes a Ga2O3-based crystal layer including a donor, and an N-doped region formed in at least a part of the Ga2O3-based crystal layer.Type: ApplicationFiled: April 26, 2018Publication date: May 7, 2020Applicants: NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY, TAMURA CORPORATION, NOVEL CRYSTAL TECHNOLOGY, INC.Inventors: Masataka HIGASHIWAKI, Yoshiaki NAKATA, Takafumi KAMIMURA, Man Hoi WONG, Kohei SASAKI, Daiki WAKIMOTO
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Patent number: 10633761Abstract: 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: GrantFiled: October 26, 2018Date of Patent: April 28, 2020Assignee: TAMURA CORPORATIONInventor: Kohei Sasaki
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Publication number: 20200066921Abstract: A trench MOS 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, a cathode electrode formed on a surface of the first semiconductor layer, an insulating film covering an inner surface of the trench, and a trench MOS gate that is buried in the trench so as to be covered with the insulating film and is in contact with the anode electrode. The second semiconductor layer includes a lower layer on a side of the first semiconductor layer and an upper layer on a side of the anode electrode having a higher donor concentration than the lower layer.Type: ApplicationFiled: February 27, 2018Publication date: February 27, 2020Applicants: TAMURA CORPORATION, NOVEL CRYSTAL TECHNOLOGY, INC.Inventors: Kohei SASAKI, Masataka HIGASHIWAKI
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Publication number: 20190363197Abstract: Provided is a Schottky barrier diode which is configured from a Ga2O3-based semiconductor, and has a lower rising voltage than a conventional one. In one embodiment, the Schottky barrier diode 1 is provided which has: a semiconductor layer 10 configured from a Ga2O3-based single crystal; an anode electrode 11 which forms a Schottky junction with the semiconductor layer 10, and has a portion which contacts the semiconductor layer 10 and is composed of Fe or Cu; and a cathode electrode 12.Type: ApplicationFiled: February 19, 2018Publication date: November 28, 2019Applicants: TAMURA CORPORATION, NOVEL CRYSTAL TECHNOLOGY, INC.Inventors: Kohei SASAKI, Daiki WAKIMOTO, Yuki KOISHIKAWA, Quang Tu THIEU
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Patent number: 10358742Abstract: 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: GrantFiled: June 2, 2017Date of Patent: July 23, 2019Assignees: TAMURA CORPORATION, Novel Crystal Technology, Inc.Inventors: Kohei Sasaki, Daiki Wakimoto
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Publication number: 20190148563Abstract: 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: ApplicationFiled: April 20, 2017Publication date: May 16, 2019Applicants: TAMURA CORPORATION, National Institute of Information and Communications TechnologyInventors: Kohei SASAKI, Masataka HIGASHIWAKI