Patents by Inventor Hirokazu Fujiwara
Hirokazu Fujiwara 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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Patent number: 8440524Abstract: A method for manufacturing a semiconductor device including a semiconductor substrate composed of silicon carbide, an upper surface electrode which contacts an upper surface of the substrate, and a lower surface electrode which contacts a lower surface of the substrate, the method including steps of: (a) forming an upper surface structure on the upper surface side of the substrate, and (b) forming a lower surface structure on the lower surface side of the substrate. The step (a) comprises steps of: (a1) depositing an upper surface electrode material layer on the upper surface of the substrate, the upper surface electrode material layer being a raw material layer of the upper surface electrode, and (a2) annealing the upper surface electrode material layer.Type: GrantFiled: February 18, 2011Date of Patent: May 14, 2013Assignees: Toyota Jidosha Kabushiki Kaisha, Denso CorporationInventors: Hirokazu Fujiwara, Masaki Konishi, Jun Kawai, Takeo Yamamoto, Takeshi Endo, Takashi Katsuno, Yukihiko Watanabe, Narumasa Soejima
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Patent number: 8436365Abstract: A SiC semiconductor device having a Schottky barrier diode includes: a substrate made of SiC and having a first conductive type, wherein the substrate includes a main surface and a rear surface; a drift layer made of SiC and having the first conductive type, wherein the drift layer is disposed on the main surface of the substrate and has an impurity concentration lower than the substrate; a Schottky electrode disposed on the drift layer and has a Schottky contact with a surface of the drift layer; and an ohmic electrode disposed on the rear surface of the substrate. The Schottky electrode directly contacts the drift layer in such a manner that a lattice of the Schottky electrode is matched with a lattice of the drift layer.Type: GrantFiled: February 21, 2011Date of Patent: May 7, 2013Assignees: DENSO CORPORATION, Toyota Jidosha Kabushiki KaishaInventors: Takeo Yamamoto, Takeshi Endo, Jun Morimoto, Hirokazu Fujiwara, Yukihiko Watanabe, Takashi Katsuno, Tsuyoshi Ishikawa
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Publication number: 20130105889Abstract: A method for manufacturing a switching device, which includes a trench type gate electrode and first to fourth semiconductor regions, is provided. The first semiconductor region is in contact with a gate insulating film and is of n-type. The second semiconductor region is in contact with the gate insulating film, and is of p-type. The third semiconductor region is in contact with the gate insulating film, and is of n-type. The fourth semiconductor region is a p-type semiconductor region which is positioned in a range deeper than the second semiconductor region and consecutive with the second semiconductor region, and which faces the gate insulating film via the third semiconductor region. The manufacturing method includes forming the second semiconductor region in which aluminum is doped, and implanting boron into a range in which the fourth semiconductor region is to be formed in the semiconductor substrate.Type: ApplicationFiled: September 14, 2012Publication date: May 2, 2013Applicants: DENSO CORPORATION, TOYOTA JIDOSHA KABUSHIKI KAISHAInventors: Hirokazu FUJIWARA, Hisashi ISHIMABUSHI, Yukihiko WATANABE, Narumasa SOEJIMA, Toshimasa YAMAMOTO, Yuuichi TAKEUCHI
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Patent number: 8324704Abstract: A silicon carbide semiconductor device with a Schottky barrier diode includes a first conductivity type silicon carbide substrate, a first conductivity type silicon carbide drift layer on a first surface of the substrate, a Schottky electrode forming a Schottky contact with the drift layer, and an ohmic electrode on a second surface of the substrate. The Schottky electrode includes an oxide layer in direct contact with the drift layer. The oxide layer is made of an oxide of molybdenum, titanium, nickel, or an alloy of at least two of these elements.Type: GrantFiled: March 23, 2010Date of Patent: December 4, 2012Assignees: DENSO CORPORATION, Toyota Jidosha Kabushiki KaishaInventors: Takeo Yamamoto, Takeshi Endo, Eiichi Okuno, Hirokazu Fujiwara, Masaki Konishi, Takashi Katsuno, Yukihiko Watanabe
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Patent number: 8216667Abstract: This invention provides a tantalum carbide-coated carbon material, which has excellent corrosion resistance to reducing gases and thermal shock resistance at high temperatures, and a process for producing the same. The tantalum carbide-coated carbon material comprises a carbon substrate and a coating film provided on the carbon substrate directly or through an intermediate layer. The coating film is formed of a large number of densely aggregated fine crystals of tantalum carbide. The diffraction line of the (220) plane of tantalum carbide shows the maximum diffraction intensity in an X-ray diffraction pattern of the coating film. More preferably, this diffraction intensity is not less than four times the intensity of a diffraction line showing the second highest diffraction intensity.Type: GrantFiled: February 7, 2006Date of Patent: July 10, 2012Assignee: Toyo Tanso Co., Ltd.Inventors: Hirokazu Fujiwara, Norimasa Yamada, Yoshihisa Abe
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Patent number: 8168485Abstract: A method of making a semiconductor device includes forming a p-type semiconductor region to an n-type semiconductor substrate in such a manner that the p-type semiconductor region is partially exposed to a top surface of the semiconductor substrate, forming a Schottky electrode of a first material in such a manner that the Schottky electrode is in Schottky contact with an n-type semiconductor region exposed to the top surface of the semiconductor substrate, and forming an ohmic electrode of a second material different from the first material in such a manner that the ohmic electrode is in ohmic contact with the exposed p-type semiconductor region. The Schottky electrode is formed earlier than the ohmic electrode.Type: GrantFiled: August 4, 2009Date of Patent: May 1, 2012Assignee: DENSO CORPORATIONInventors: Takeshi Endo, Eiichi Okuno, Takeo Yamamoto, Hirokazu Fujiwara, Masaki Konishi, Yukihiko Watanabe, Takashi Katsuno
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Patent number: 8164100Abstract: A semiconductor device is provided in which the contact resistance of the interface between an electrode and the semiconductor substrate is reduced. The semiconductor device includes a 4H polytype SiC substrate, and an electrode formed on a surface of the substrate. A 3C polytype layer, which extends obliquely relative to the surface of the substrate and whose end portion at the substrate surface is in contact with the electrode, is formed at the surface of the substrate. The 3C polytype layer has a lower bandgap than 4H polytype. Hence, electrons present in the 4H polytype region pass through the 3C polytype layer and reach the electrode. More precisely, the width of the passageway of the electrons is determined by the thickness of the 3C polytype layer. Consequently, with this semiconductor device, in which the passageway of the electrons is narrow, the electrons are able to reach the electrode at a speed close to the theoretical value, by the quantum wire effect.Type: GrantFiled: December 18, 2008Date of Patent: April 24, 2012Assignees: Toyota Jidosha Kabushiki Kaisha, Denso CorporationInventors: Hirokazu Fujiwara, Masaki Konishi, Eiichi Okuno
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Patent number: 8163637Abstract: First, a first layer made of Ni or an alloy including Ni may be formed on an upper surface of a semiconductor layer. Next, a second layer made of silicon oxide may be formed on an upper surface of the first layer. Next, a part, which corresponds to a semiconductor region, of the second layer may be removed. Next, second conductive type ion impurities may be injected from upper sides of the first and second layers to the semiconductor layer after the removing step.Type: GrantFiled: December 22, 2010Date of Patent: April 24, 2012Assignees: Toyota Jidosha Kabushiki Kaisha, Denso CorporationInventors: Masaki Konishi, Hirokazu Fujiwara, Takeshi Endo, Takeo Yamamoto, Takashi Katsuno, Yukihiko Watanabe
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Publication number: 20120052642Abstract: A method of manufacturing a semiconductor device includes forming a drift layer on a substrate; forming a base layer on the drift layer; forming a trench to penetrate the base layer and to reach the drift layer; rounding off a part of a shoulder corner and a part of a bottom corner of the trench; covering an inner wall of the trench with an organic film; implanting an impurity to a surface portion of the base layer; forming a source region by activating the implanted impurity; and removing the organic film after the source region is formed, in which the substrate, the drift layer, the base layer and the source region are made of silicon carbide, and the implanting and the activating of the impurity are performed under a condition that the trench is covered with the organic film.Type: ApplicationFiled: August 30, 2011Publication date: March 1, 2012Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA, DENSO CORPORATIONInventors: Takeshi ENDO, Shinichiro MIYAHARA, Tomoo MORINO, Masaki KONISHI, Hirokazu FUJIWARA, Jun MORIMOTO, Tsuyoshi ISHIKAWA, Takashi KATSUNO, Yukihiko WATANABE
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Publication number: 20120040172Abstract: The problem of the present invention is provision of a tantalum carbide-coated carbon material having superior corrosion resistance to reducing gas and superior resistance to thermal shock at a high temperature and a production method thereof. According to the present invention, a tantalum carbide-coated carbon material having a carbon substrate and a coating film formed directly or via an intermediate layer on the aforementioned carbon substrate can be provided. The coating film consists of a number of microcrystals of tantalum carbide, which are densely gathered and, in an X-ray diffraction pattern of the coating film, the diffraction intensity of the (220) plane of tantalum carbide preferably shows the maximum level, more preferably, the aforementioned diffraction intensity is not less than 4 times the intensity of the second highest diffraction intensity.Type: ApplicationFiled: February 7, 2006Publication date: February 16, 2012Inventors: Hirokazu Fujiwara, Norimasa Yamada, Yoshihisa Abe
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Publication number: 20110207321Abstract: A method for manufacturing a semiconductor device including a semiconductor substrate composed of silicon carbide, an upper surface electrode which contacts an upper surface of the substrate, and a lower surface electrode which contacts a lower surface of the substrate, the method including steps of: (a) forming an upper surface structure on the upper surface side of the substrate, and (b) forming a lower surface structure on the lower surface side of the substrate. The step (a) comprises steps of: (a1) depositing an upper surface electrode material layer on the upper surface of the substrate, the upper surface electrode material layer being a raw material layer of the upper surface electrode, and (a2) annealing the upper surface electrode material layer.Type: ApplicationFiled: February 18, 2011Publication date: August 25, 2011Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA, DENSO CORPORATIONInventors: Hirokazu FUJIWARA, Masaki KONISHI, Jun KAWAI, Takeo YAMAMOTO, Takeshi ENDO, Takashi KATSUNO, Yukihiko WATANABE, Narumasa SOEJIMA
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Publication number: 20110204383Abstract: A SiC semiconductor device having a Schottky barrier diode includes: a substrate made of SiC and having a first conductive type, wherein the substrate includes a main surface and a rear surface; a drift layer made of SiC and having the first conductive type, wherein the drift layer is disposed on the main surface of the substrate and has an impurity concentration lower than the substrate; a Schottky electrode disposed on the drift layer and has a Schottky contact with a surface of the drift layer; and an ohmic electrode disposed on the rear surface of the substrate. The Schottky electrode directly contacts the drift layer in such a manner that a lattice of the Schottky electrode is matched with a lattice of the drift layer.Type: ApplicationFiled: February 21, 2011Publication date: August 25, 2011Applicants: DENSO CORPORATION, TOYOTA JIDOSHA KABUSHIKI KAISHAInventors: Takeo YAMAMOTO, Takeshi Endo, Jun Morimoto, Hirokazu Fujiwara, Yukihiko Watanabe, Takashi Katsuno, Tsuyoshi Ishikawa
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Publication number: 20110151654Abstract: First, a first layer made of Ni or an alloy including Ni may be formed on an upper surface of a semiconductor layer. Next, a second layer made of silicon oxide may be formed on an upper surface of the first layer. Next, a part, which corresponds to a semiconductor region, of the second layer may be removed. Next, second conductive type ion impurities may be injected from upper sides of the first and second layers to the semiconductor layer after the removing step.Type: ApplicationFiled: December 22, 2010Publication date: June 23, 2011Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA, DENSO CORPORATIONInventors: Masaki KONISHI, Hirokazu FUJIWARA, Takeshi ENDO, Takeo YAMAMOTO, Takashi KATSUNO, Yukihiko WATANABE
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Patent number: 7855131Abstract: A manufacturing method of a semiconductor device comprises a process of doping conductive impurities in a silicon carbide substrate, a process of forming a cap layer on a surface of the silicon carbide substrate, a process of activating the conductive impurities doped in the silicon carbide substrate, a process of oxidizing the cap layer after a first annealing process, and a process of removing the oxidized cap layer. It is preferred that the cap layer is formed from material that includes metal carbide. Since the oxidation onset temperature of metal carbide is comparatively low, the oxidization of the cap layer becomes easy if metal carbide is included in the cap layer. Specifically, it is preferred that the cap layer is formed from metal carbide that has an oxidation onset temperature of 1000 degrees Celsius or below, such as tantalum carbide.Type: GrantFiled: April 20, 2009Date of Patent: December 21, 2010Assignees: Toyota Jidosha Kabushiki Kaisha, Denso CorporationInventors: Hirokazu Fujiwara, Masaki Konishi, Takeo Yamamoto, Eiichi Okuno, Yukihiko Watanbe, Takashi Katsuno
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Publication number: 20100244049Abstract: A silicon carbide semiconductor device with a Schottky barrier diode includes a first conductivity type silicon carbide substrate, a first conductivity type silicon carbide drift layer on a first surface of the substrate, a Schottky electrode forming a Schottky contact with the drift layer, and an ohmic electrode on a second surface of the substrate. The Schottky electrode includes an oxide layer in direct contact with the drift layer. The oxide layer is made of an oxide of molybdenum, titanium, nickel, or an alloy of at least two of these elements.Type: ApplicationFiled: March 23, 2010Publication date: September 30, 2010Applicants: DENSO CORPORATION, TOYOTA JIDOSHA KABUSHIKI KAISHAInventors: Takeo Yamamoto, Takeshi Endo, Eiichi Okuno, Hirokazu Fujiwara, Masaki Konishi, Takashi Katsuno, Yukihiko Watanabe
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Patent number: 7779392Abstract: Object information is read that denotes a load state of the object from storage and selects an object having a load that is lower than a predetermined value. Then, a reference to an object allocation control part is returned that allocates the selected object to a destination as a response through communicating means. In allocating an object, the object information is read from the storage to select an object having a load that is lower than a predetermined value. Then, a reference to a dispatcher is returned that executes the selected object to the destination as a response through the communicating means. In executing the object, the object information is read from the storage and executes the object if the object has a load that is lower than a predetermined threshold value.Type: GrantFiled: November 30, 2004Date of Patent: August 17, 2010Assignee: Hitachi, Ltd.Inventors: Atsushi Sashino, Tomohiko Shigeoka, Hirokazu Fujiwara, Atsuhiro Yokoro, Akio Igarashi
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Publication number: 20100032730Abstract: A method of making a semiconductor device includes forming a p-type semiconductor region to an n-type semiconductor substrate in such a manner that the p-type semiconductor region is partially exposed to a top surface of the semiconductor substrate, forming a Schottky electrode of a first material in such a manner that the Schottky electrode is in Schottky contact with an n-type semiconductor region exposed to the top surface of the semiconductor substrate, and forming an ohmic electrode of a second material different from the first material in such a manner that the ohmic electrode is in ohmic contact with the exposed p-type semiconductor region. The Schottky electrode is formed earlier than the ohmic electrode.Type: ApplicationFiled: August 4, 2009Publication date: February 11, 2010Applicant: DENSO CORPORATIONInventors: Takeshi Endo, Eiichi Okuno, Takeo Yamamoto, Hirokazu Fujiwara, Masaki Konishi, Yukihiko Watanabe, Takashi Katsuno
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Publication number: 20090269908Abstract: A manufacturing method of a semiconductor device comprises a process of doping conductive impurities in a silicon carbide substrate, a process of forming a cap layer on a surface of the silicon carbide substrate, a process of activating the conductive impurities doped in the silicon carbide substrate, a process of oxidizing the cap layer after a first annealing process, and a process of removing the oxidized cap layer. It is preferred that the cap layer is formed from material that includes metal carbide. Since the oxidation onset temperature of metal carbide is comparatively low, the oxidization of the cap layer becomes easy if metal carbide is included in the cap layer. Specifically, it is preferred that the cap layer is formed from metal carbide that has an oxidation onset temperature of 1000 degrees Celsius or below, such as tantalum carbide.Type: ApplicationFiled: April 20, 2009Publication date: October 29, 2009Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA, DENSO CORPORATIONInventors: Hirokazu Fujiwara, Masaki Konishi, Takeo Yamamoto, Eiichi Okuno, Yukihiko Watanabe, Takashi Katsuno
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Publication number: 20090267082Abstract: A semiconductor device includes: a semiconductor element having a first surface and a second surface; a first electrode disposed on the first surface of the element; a second electrode disposed on the second surface of the element; and an insulation film covers a part of the first electrode, the first surface of the element and a part of a sidewall of the element. The above semiconductor device has small dimensions and a high breakdown voltage.Type: ApplicationFiled: April 14, 2009Publication date: October 29, 2009Applicant: DENSO CORPORATIONInventors: Takeo Yamamoto, Takeshi Endo, Eiichi Okuno, Masaki Konishi, Hirokazu Fujiwara
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Publication number: 20090230405Abstract: A manufacturing method of a diode includes: forming a P type semiconductor film on a N type semiconductor layer with a crystal growth method; forming a first metallic film on the P type semiconductor film so that the first metallic film contacts the P type semiconductor film with an ohmic contact; forming a mask having an opening on the first metallic film; etching a part of the first metallic film and a part of the P type semiconductor film via the opening so that a part of the N type semiconductor layer is exposed; and forming a second metallic film on the part of the N type semiconductor layer so that the second metallic film contacts the N type semiconductor layer with a Schottky contact.Type: ApplicationFiled: March 13, 2009Publication date: September 17, 2009Applicant: DENSO CORPORATIONInventors: Takeo Yamamoto, Takeshi Endo, Masaki Konishi, Hirokazu Fujiwara, Yukihiko Watanabe, Takashi Katsuno, Masayasu Ishiko