Patents by Inventor Tomoki Oku

Tomoki Oku 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: 7135416
    Abstract: A method of manufacturing a semiconductor device including a gallium nitride related semiconductor. The method include preparing a substrate having surface of a gallium nitride related semiconductor; contacting the surface with atomic nitrogen, which is obtained by decomposing a nitrogen-containing gas in a catalytic reaction, to nitride the surface; and forming, on the surface, a gate electrode and source and drain electrodes opposing each other across the gate electrode.
    Type: Grant
    Filed: February 25, 2004
    Date of Patent: November 14, 2006
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Masahiro Totsuka, Tomoki Oku
  • Publication number: 20060231871
    Abstract: A gate electrode serving as a Schottky electrode includes a TaNx layer and an Au layer. The TaNx layer serves as a barrier metal for preventing atoms from diffusing from the Au layer into a substrate. TaNx does not contain Si, and therefore has a higher humidity resistance than WSiN containing Si. Accordingly, the gate electrode has a higher humidity resistance than a conventional gate electrode including a WSiN layer. Setting a nitrogen content at less than 0.8 can prevent significant degradation in Schottky characteristics as compared to the conventional gate electrode. Setting the nitrogen content at 0.5 or less, Schottky characteristics can be improved more than in the conventional gate electrode.
    Type: Application
    Filed: March 14, 2006
    Publication date: October 19, 2006
    Applicant: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Hirotaka Amasuga, Toshihiko Shiga, Tetsuo Kunii, Tomoki Oku
  • Patent number: 6933250
    Abstract: A process of manufacturing a semiconductor device uses catalytic chemical vapor deposition. In the process, a reaction chamber containing a catalyzer and a substrate has gasses, including silane, ammonia, and hydrogen supplied to the reaction chamber. The gases are brought into contact with the catalyzer and then with the substrate to deposit a silicon nitride film.
    Type: Grant
    Filed: October 21, 2002
    Date of Patent: August 23, 2005
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Masahiro Totsuka, Tomoki Oku, Ryo Hattori
  • Publication number: 20040224529
    Abstract: A method of manufacturing a semiconductor device including a gallium nitride related semiconductor. The method include preparing a substrate having surface of a gallium nitride related semiconductor; contacting the surface with atomic nitrogen, which is obtained by decomposing a nitrogen-containing gas in a catalytic reaction, to nitride the surface; and forming, on the surface, a gate electrode and source and drain electrodes opposing each other across the gate electrode.
    Type: Application
    Filed: February 25, 2004
    Publication date: November 11, 2004
    Applicant: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Masahiro Totsuka, Tomoki Oku
  • Publication number: 20030198743
    Abstract: The present invention is to provide a silicon nitride film forming apparatus and a forming method which makes possible the high reproducibility of film quality or film thickness. The silicon nitride film forming apparatus and forming method in which a heating element and a substrate are arranged in a vacuum vessel connected to a gas exhaust system and a gas supply system to deposit a silicon nitride film on the substrate surface by maintaining the heating element at a predetermined temperature and by decomposing and/or activating a raw material gas supplied from the gas supply system, comprises: an inner wall which is arranged in the vacuum vessel surrounding the heating element and the substrate so as to form a film formation space, a gas introduction means to introduce the raw material gas to the film forming space, and at least one of a heating means and a cooling means of the inner wall arranged to control the inner wall to a predetermined temperature.
    Type: Application
    Filed: April 22, 2003
    Publication date: October 23, 2003
    Inventors: Hitoshi Morisaki, Yasushi Kamiya, Shuji Nomura, Masahiro Totuka, Tomoki Oku, Ryo Hattori
  • Publication number: 20030194881
    Abstract: A process of manufacturing a semiconductor device uses catalytic chemical vapor deposition process, and has three steps. In the process, a reaction chamber (10) including a catalyzer (6) and a substrate (1) therein is provided. Gases including silane gas, ammonia gas, and hydrogen gas are provided. The gases are supplied to the reaction chamber, the gases are brought into contact with the catalyzer, and then towards onto the substrate to deposit the silicon nitride film.
    Type: Application
    Filed: October 21, 2002
    Publication date: October 16, 2003
    Applicant: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Masahiro Totsuka, Tomoki Oku, Ryo Hattori
  • Patent number: 6013926
    Abstract: A semiconductor device includes a self-aligned refractory metal constituent in a recess in a semiconductor substrate and having the same plane pattern as a bottom surface of the recess. The width of the constituent is determined by the plane pattern of the recess and, accordingly, the pattern width of the constituent is easily controlled by the plane pattern of the recess.
    Type: Grant
    Filed: April 18, 1997
    Date of Patent: January 11, 2000
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Naohito Yoshida, Shinichi Miyakuni, Toshihiko Shiga
  • Patent number: 5888859
    Abstract: A method of making a semiconductor device includes forming a recess in a compound semiconductor substrate using a patterned insulating film on a surface of the substrate, implanting dopant ions at the bottom of the recess to form a channel region, and depositing a refractory metal film. The refractory metal film is etched, using a resist pattern, to form a gate electrode and additional dopant ions are implanted to form relatively highly doped regions intersecting the channel region. Very highly doped regions are formed my implantation, after removing the insulating film, using the gate electrode and remainder of the resist mask as an implantation mask. After stripping the resist, annealing to activate the implanted ions, and depositing a passivating film on the substrate and gate electrode, source and drain electrodes are formed.
    Type: Grant
    Filed: November 15, 1996
    Date of Patent: March 30, 1999
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Shinichi Miyakuni, Nobuyuki Kasai, Yasutaka Kohno, deceased
  • Patent number: 5812364
    Abstract: An MIM capacitor includes a lower electrode; a first insulating film disposed on the lower electrode; a second insulating film disposed on the first insulating film and having a first opening exposing a portion of the surface of the first insulating film on the lower electrode, the first opening having a perimeter; a third insulating film disposed on the second insulating film and having a second opening exposing a portion of the surface of the second insulating film, the second opening having a perimeter that surrounds the perimeter of the first opening on the second insulating film; and an upper electrode disposed on the first insulating film through the first opening and extending onto the second insulating film.
    Type: Grant
    Filed: January 15, 1997
    Date of Patent: September 22, 1998
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Takahide Ishikawa
  • Patent number: 5726468
    Abstract: A semiconductor device includes a semiconductor substrate; a first active layer disposed on the semiconductor substrate; a second active layer disposed on the first active layer; a first electrode including a lower stage disposed on the second active layer and an upper stage disposed on the lower stage and having an overhanging portion protruding from the lower stage; an insulating film continuously covering a surface of the second active layer, a side surface of the lower stage of the first electrode, and a lower surface and a side surface of the overhanging portion of the upper stage; and a second electrode disposed on the surface of the first active layer at opposite sides of the second active layer, self-aligned with the second active layer. The distance between the second electrode and the second active layer is minimized and the thickness of the second electrode can be about 7000 .ANG., minimizing the resistance of the first active layer and improving high frequency characteristics.
    Type: Grant
    Filed: March 13, 1996
    Date of Patent: March 10, 1998
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Hirofumi Nakano, Shinichi Miyakuni, Teruyuki Shimura, Ryo Hattori
  • Patent number: 5675159
    Abstract: A semiconductor device includes a compound semiconductor body having a recess, the recess having a bottom and a hollow, and a refractory metal gate electrode having a lower portion within the hollow. The compound semiconductor body includes a compound semiconductor substrate; a channel layer including a compound semiconductor of a first conductivity type, the channel layer being located on the substrate between the gate electrode and the substrate; first active layers of the compound semiconductor and of the first conductivity type located on regions of the substrate in the recess where the channel layer is not present; and second active layers of the compound semiconductor and of the first conductivity type located on regions of the substrate in the recess where the channel layer is not present; and second active layers of the compound semiconductor of the first conductivity type located on regions of the substrate sandwiching the recess.
    Type: Grant
    Filed: January 5, 1996
    Date of Patent: October 7, 1997
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Nobuyuki Kasai
  • Patent number: 5538910
    Abstract: A method of producing a field effect transistor that includes forming a step in a compound semiconductor substrate, forming a first insulating side wall at the step, forming an etch blocking layer on the substrate, removing the first insulating side wall, and etching the substrate not protected by the etch blocking layer to produce a recess. Subsequently, a second insulating side wall is formed at the sides of the recess, a refractory metal and a low resistance metal are sequentially deposited and formed as a gate electrode, and finally, source and drain electrodes are formed.
    Type: Grant
    Filed: January 25, 1995
    Date of Patent: July 23, 1996
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Tomoki Oku
  • Patent number: 5498572
    Abstract: A method for manufacturing a semiconductor device including forming an electrode on a part of a semiconductor substrate, depositing an insulating film on the semiconductor substrate and on the electrode, and forming a contact hole penetrating through the insulating film to expose a part of the electrode; forming a barrier metal layer on the electrode in the contact hole, on the internal side surface of the contact hole, and on the surface of the insulating film; and depositing a metal layer on the barrier metal layer and patterning the metal layer and the barrier metal layer to form a wiring layer wherein the barrier metal layer comprises a metal that does not form an intermetallic material by solid state diffusion with either of the electrode and the metal layer even at elevated temperatures.
    Type: Grant
    Filed: September 30, 1994
    Date of Patent: March 12, 1996
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Toshihiko Shiga, Ryo Hattori, Tomoki Oku
  • Patent number: 5399896
    Abstract: A method for producing a T-shaped gate electrode of a semiconductor device including forming an insulating film on a semiconductor substrate, etching away a prescribed portion of the insulating film, depositing a metal film having a prescribed thickness, forming a first photoresist film and removing the photoresist film except where the insulating film has been removed, forming a second photoresist film, patterning the second photoresist film to expose the metal film along a side wall of the insulating film, etching away a portion of the metal film using the first and second photoresist films as a mask, depositing a gate metal and removing the first and second photoresist films and overlying gate metal by lift-off, and etching away the metal films remaining on the semiconductor substrate and the insulating film. Thereby, a T-shaped gate electrode with shortened length is formed.
    Type: Grant
    Filed: October 27, 1993
    Date of Patent: March 21, 1995
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Tomoki Oku
  • Patent number: 5387529
    Abstract: A particle beam irradiates a thermohardening resin and selectively hardens the thermohardening resin of the implanted region. The non-hardened resin not irradiated is removed with high selectivity and an inverted pattern of the hardened resin remains as a mask. Using the same photoresist mask employed in the irradiation for selective hardening, ion implantation through the hardened resin forms spaced apart implanted regions in the substrate. The removal of the photoresist and the non-hardened resin leaves an aperture for metal deposition to form Schottky barrier. Hardened resin from portions of spaced apart implanted regions is removed, followed by metal deposition forming source and drain electrodes to complete a MESFET. Spin-on-glass as the thermohardening resin is also disclosed.
    Type: Grant
    Filed: November 16, 1993
    Date of Patent: February 7, 1995
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Tomoki Oku
  • Patent number: 5376812
    Abstract: A method for producing a Schottky barrier gate type field effect transistor includes producing a low concentration active region at a desired position of a semi-insulating compound semiconductor substrate and producing a gate electrode comprising refractory metal on the active region, producing a first insulating film and etching the same thereby to produce first side wall assist films comprising the first insulating film at both side walls of the gate electrode, removing one of the first side wall assist films at the side where a source electrode is to be produced, depositing a second insulating film to the thickness less than that of the first insulating film, etching the second insulating film thereby to produce a second side wall assist film having narrower width than that of the first side wall assist film at the side wall of the gate electrode where the source electrode is to be produced, and conducting ion implantation using the first and second side wall assist films and the gate electrode as a mask t
    Type: Grant
    Filed: December 20, 1989
    Date of Patent: December 27, 1994
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Tomoki Oku
  • Patent number: 5358885
    Abstract: A method of producing a field effect transistor includes depositing a first insulating film and a refractory metal on a semiconductor substrate, forming a first aperture penetrating the first insulating film and the refractory metal film to provide a gate electrode production region, depositing a second insulating film on the refractory metal film, etching the second insulating film in a direction perpendicular to the surface of the substrate leaving portions of the second insulating film on opposite side walls of the first aperture to form a second aperture, defining a gate length, depositing a gate metal, and patterning the gate metal layer, the first insulating film, and the refractory metal film in a prescribed width to form a T-shaped gate structure. During etching the second insulating film, since the refractory metal film serves as a etch stopping layer, the first insulating film is not etched and its thickness remains as deposited.
    Type: Grant
    Filed: April 16, 1993
    Date of Patent: October 25, 1994
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Tomoki Oku, Masayuki Sakai, Yasutaka Kohno
  • Patent number: 5300445
    Abstract: A particle beam irradiates a thermohardening resin and selectively hardens the thermohardening resin of the implanted region. The non-hardened resin not irradiated is removed with high selectivity and an inverted pattern of the hardened resin remains as a mask. In one embodiment, a gate electrode is produced in an aperture pattern produced by transfer of the inverted pattern and source and drain electrodes are provided at other aperture patterns to form an HEMT having a narrow gate self-aligned with the source and drain electrodes.
    Type: Grant
    Filed: September 24, 1992
    Date of Patent: April 5, 1994
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Tomoki Oku
  • Patent number: 5250453
    Abstract: A method for producing a field effect transistor includes depositing an insulating film on an active layer produced in a semiconductor substrate and removing a part of the insulating film, leaving a side wall substantially perpendicular to the substrate. A refractory metal is deposited on the surface of the semiconductor substrate and the insulating film. The refractory metal is removed except for a portion at the side wall of the insulating film to produce a gate electrode. A high dopant concentration region is ion implanted using the insulating film and refractory metal as a mask. The insulating film is removed and an intermediate dopant concentration region is ion implanted using the refractory metal as a mask. A source electrode is produced on the high dopant concentration region and a drain electrode is produced on the intermediate dopant concentration region. The invention may be used to produce asymmetrically doped drain and gate regions and an asymmetrically disposed gate electrode.
    Type: Grant
    Filed: September 29, 1992
    Date of Patent: October 5, 1993
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Yasutaka Kohno, Tomoki Oku
  • Patent number: 5187112
    Abstract: A method for producing a field effect transistor includes depositing an insulating film on an active layer produced in a semiconductor substrate and removing a part of the insulating film, leaving a side wall substantially perpendicular to the substrate. A refractory metal is deposited on the surface of the semiconductor substrate and the insulating film. The refractory metal is removed except for a portion at the side wall of the insulating film to produce a gate electrode. A high dopant concentration region is ion implanted using the insulating film and refractory metal as a mask. The insulating film is removed and an intermediate dopant concentration region is ion implanted using the refractory metal as a mask. A source electrode is produced on the high dopant cocentration region and a drain electrode is produced on the intermediate dopant concentration region. The invention may be used to produce asymmetrically doped drain and gate regions and an asymmetrically disposed gate electrode.
    Type: Grant
    Filed: April 5, 1990
    Date of Patent: February 16, 1993
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Yasutaka Kohno, Tomoki Oku