Patents by Inventor Akio Wakejima

Akio Wakejima 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: 20180233590
    Abstract: In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer).
    Type: Application
    Filed: March 16, 2018
    Publication date: August 16, 2018
    Inventors: Takashi Inoue, Tatsuo Nakayama, Yuji Ando, Yasuhiro Murase, Kazuki Ota, Hironobu Miyamoto, Katsumi Yamanoguchi, Naotaka Kuroda, Akio Wakejima, Yasuhiro Okamoto
  • Patent number: 9954087
    Abstract: In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer).
    Type: Grant
    Filed: August 27, 2014
    Date of Patent: April 24, 2018
    Assignee: RENESAS ELECTRONICS CORPORATION
    Inventors: Takashi Inoue, Tatsuo Nakayama, Yuji Ando, Yasuhiro Murase, Kazuki Ota, Hironobu Miyamoto, Katsumi Yamanoguchi, Naotaka Kuroda, Akio Wakejima, Yasuhiro Okamoto
  • Publication number: 20140367743
    Abstract: In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer).
    Type: Application
    Filed: August 27, 2014
    Publication date: December 18, 2014
    Inventors: Takashi Inoue, Tatsuo Nakayama, Yuji Ando, Yasuhiro Murase, Kazuki Ota, Hironobu Miyamoto, Katsumi Yamanoguchi, Naotaka Kuroda, Akio Wakejima, Yasuhiro Okamoto
  • Patent number: 8853666
    Abstract: In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer).
    Type: Grant
    Filed: October 25, 2006
    Date of Patent: October 7, 2014
    Assignee: Renesas Electronics Corporation
    Inventors: Takashi Inoue, Tatsuo Nakayama, Yuji Ando, Yasuhiro Murase, Kazuki Ota, Hironobu Miyamoto, Katsumi Yamanoguchi, Naotaka Kuroda, Akio Wakejima, Yasuhiro Okamoto
  • Patent number: 8476980
    Abstract: A power amplifier includes an amplifying circuit, and first through third transmission lines. The amplifying circuit amplifies an input signal having a fundamental frequency to generate a first amplified signal and a second amplified signal whose phase is opposed to the first amplified signal. The first transmission line adds a first group of phases, different in correspondence with a frequency, to the first amplified signal by using a left-handed material to generate a first transmission signal. The second transmission line adds a second group of phases, different in correspondence with a frequency, to the second amplified signal by using a right-handed material to generate a second transmission signal. The third transmission line overlaps the first and the second transmission signals to generate an output signal. The first and the second group of phases include a phase difference configured to weaken a second harmonic and a third harmonic.
    Type: Grant
    Filed: February 3, 2010
    Date of Patent: July 2, 2013
    Assignee: NEC Corporation
    Inventor: Akio Wakejima
  • Patent number: 8476756
    Abstract: A semiconductor device includes a semiconductor element having a rectangular two-dimensional geometry and serving as a heat source, a first heat sink section including the semiconductor element mounted thereon, and a second heat sink section joined to an opposite side of the first heat sink section that includes the semiconductor element. A relation among directional components of thermal conductivity is K1yy?K1xx>K1zz, where directional components of a three-dimensional thermal conductivity of the heat sink section in X, Y, and Z directions are determined as Kxx, Kyy, and Kzz. A relation among directional components of a thermal conductivity of the second heat sink section is K2zz?K2yy>K2xx or K2yy?K2zz>K2xx, where the directional components of the thermal conductivity of the second heat sink section in X, Y, and X directions are determined as K2xx, K2yy, and K2zz.
    Type: Grant
    Filed: September 21, 2011
    Date of Patent: July 2, 2013
    Assignee: NEC Corporation
    Inventors: Naotaka Kuroda, Akio Wakejima, Masahiro Tanomura, Hironobu Miyamoto
  • Patent number: 8466495
    Abstract: Disclosed is an HJFET 110 which comprises: a channel layer 12 composed of InyGa1-yN (0?y?1); a carrier supply layer 13 composed of AlxGa1-xN (0?x?1), the carrier supply layer 13 being provided over the channel layer 12 and including at least one p-type layer; and a source electrode 15S, a drain electrode 15D and a gate electrode 17 which are disposed facing the channel layer 12 through the p-type layer, and provided over the carrier supply layer 13. The following relational expression is satisfied: 5.6×1011x<NA×?×t [cm?2]<5.6×1013x, where x denotes an Al compositional ratio of said carrier supply layer, t denotes a thickness of said p-type layer, NA denotes an impurity concentration, and ? denotes an activation ratio.
    Type: Grant
    Filed: May 10, 2012
    Date of Patent: June 18, 2013
    Assignee: NEC Corporation
    Inventors: Yuji Ando, Hironobu Miyamoto, Tatsuo Nakayama, Yasuhiro Okamoto, Takashi Inoue, Yasuhiro Murase, Kazuki Ota, Akio Wakejima, Naotaka Kuroda
  • Publication number: 20120217547
    Abstract: Disclosed is an HJFET 110 which comprises: a channel layer 12 composed of InyGa1-yN (0?y?1); a carrier supply layer 13 composed of AlxGa1-xN (0?x?1), the carrier supply layer 13 being provided over the channel layer 12 and including at least one p-type layer; and a source electrode 15S, a drain electrode 15D and a gate electrode 17 which are disposed facing the channel layer 12 through the p-type layer, and provided over the carrier supply layer 13. The following relational expression is satisfied: 5.6×1011x<NA×?×t [cm?2]<5.6×1013x, where x denotes an Al compositional ratio of said carrier supply layer, t denotes a thickness of said p-type layer, NA denotes an impurity concentration, and ? denotes an activation ratio.
    Type: Application
    Filed: May 10, 2012
    Publication date: August 30, 2012
    Applicant: NEC CORPORATION
    Inventors: Yuji ANDO, Hironobu MIYAMOTO, Tatsuo NAKAYAMA, Yasuhiro OKAMOTO, Takashi INOUE, Yasuhiro MURASE, Kazuki OTA, Akio WAKEJIMA, Naotaka KURODA
  • Publication number: 20120188010
    Abstract: A power amplifier includes an amplifying circuit, and first through third transmission lines. The amplifying circuit amplifies an input signal having a fundamental frequency to generate a first amplified signal and a second amplified signal whose phase is opposed to the first amplified signal. The first transmission line adds a first group of phases, different in correspondence with a frequency, to the first amplified signal by using a left-handed material to generate a first transmission signal. The second transmission line adds a second group of phases, different in correspondence with a frequency, to the second amplified signal by using a right-handed material to generate a second transmission signal. The third transmission line overlaps the first and the second transmission signals to generate an output signal. The first and the second group of phases include a phase difference configured to weaken a second harmonic and a third harmonic.
    Type: Application
    Filed: February 3, 2010
    Publication date: July 26, 2012
    Applicant: NEC CORPORATION
    Inventor: Akio Wakejima
  • Patent number: 8198652
    Abstract: Disclosed is an HJFET 110 which comprises: a channel layer 12 composed of InyGa1-yN (0?y?1); a carrier supply layer 13 composed of AlxGa1-xN (0?x?1), the carrier supply layer 13 being provided over the channel layer 12 and including at least one p-type layer; and a source electrode 15S, a drain electrode 15D and a gate electrode 17 which are disposed facing the channel layer 12 through the p-type layer, and provided over the carrier supply layer 13. The following relational expression is satisfied: 5.6×1011x<NA×?×t [cm?2]<5.6×1013x, where x denotes an Al compositional ratio of the carrier supply layer, t denotes a thickness of the p-type layer, NA denotes an impurity concentration, and ? denotes an activation ratio.
    Type: Grant
    Filed: March 29, 2007
    Date of Patent: June 12, 2012
    Assignee: NEC Corporation
    Inventors: Yuji Ando, Hironobu Miyamoto, Tatsuo Nakayama, Yasuhiro Okamoto, Takashi Inoue, Yasuhiro Murase, Kazuki Ota, Akio Wakejima, Naotaka Kuroda
  • Publication number: 20120012995
    Abstract: A semiconductor device includes a semiconductor element having a rectangular two-dimensional geometry and serving as a heat source, a first heat sink section including the semiconductor element mounted thereon, and a second heat sink section joined to an opposite side of the first heat sink section that includes the semiconductor element. A relation among directional components of thermal conductivity is K1yy?K1xx>K1zz, where directional components of a three-dimensional thermal conductivity of the heat sink section in X, Y, and Z directions are determined as Kxx, Kyy, and Kzz. A relation among directional components of a thermal conductivity of the second heat sink section is K2zz?K2yy>K2xx or K2yy?K2zz>K2xx, where the directional components of the thermal conductivity of the second heat sink section in X, Y, and X directions are determined as K2xx, K2yy, and K2zz.
    Type: Application
    Filed: September 21, 2011
    Publication date: January 19, 2012
    Applicant: NEC CORPORATION
    Inventors: Naotaka Kuroda, Akio Wakejima, Masahiro Tanomura, Hironobu Miyamoto
  • Patent number: 8063484
    Abstract: A semiconductor device, comprising: a semiconductor element 20 having a rectangular two-dimensional geometry and serving as a heat source; and a heat sink section 25 having the semiconductor element 20 mounted thereon, wherein a relation among the directional components of said thermal conductivity is: Kzz?Kyy>Kxx, where directional components of three-dimensional thermal conductivity of the heat sink section 25 in X, Y and Z directions are determined as Kxx, Kyy and Kzz, and where the longer side direction of the semiconductor element 20 is defined as X direction, the shorter side direction thereof is defined as Y direction and the thickness direction is defined as Z direction.
    Type: Grant
    Filed: October 25, 2007
    Date of Patent: November 22, 2011
    Assignee: NEC Corporation
    Inventors: Naotaka Kuroda, Akio Wakejima, Masahiro Tanomura, Hironobu Miyamoto
  • Patent number: 7863648
    Abstract: A field effect transistor (100) exhibiting good performance at high voltage operation and high frequency includes a first field plate electrode (116) and a second field plate electrode (118). The second field plate electrode includes a shielding part (119) located in the region between the first field plate electrode and a drain electrode (114), and serves to shield the first field plate electrode from the drain electrode. When in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region where the second field plate electrode (118) overlap the upper part of a structure including the first field plate electrode and a gate electrode (113) is designated as Lol, and the gate length is Lg, the relation expressed as 0 ?Lol/Lg?1 holds.
    Type: Grant
    Filed: June 12, 2006
    Date of Patent: January 4, 2011
    Assignee: NEC Corporation
    Inventors: Hironobu Miyamoto, Yuji Ando, Yasuhiro Okamoto, Tatsuo Nakayama, Takashi Inoue, Kazuki Ota, Akio Wakejima, Kensuke Kasahara, Yasuhiro Murase, Kohji Matsunaga, Katsumi Yamanoguchi, Hidenori Shimawaki
  • Patent number: 7800131
    Abstract: A field effect transistor includes a layer structure made of compound semiconductor (111) provided on a semiconductor substrate (110) made of GaAs or InP, as an operation layer, and employs a first field plate electrode (116) and a second field plate electrode (118). The second field plate electrode includes a shielding part (119) located in the region between the first field plate electrode and a drain electrode (114), and serves to shield the first field plate electrode from the drain electrode. When, in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region, in which the second field plate electrode overlaps the upper part of a structure composed of the first field plate electrode and a gate electrode (113), is designated as Lol, and the gate length is Lg, the relation expressed as 0?Lol/Lg?1 holds.
    Type: Grant
    Filed: June 12, 2006
    Date of Patent: September 21, 2010
    Assignee: NEC Corporation
    Inventors: Hironobu Miyamoto, Yuji Ando, Yasuhiro Okamoto, Tatsuo Nakayama, Takashi Inoue, Kazuki Ota, Akio Wakejima, Kensuke Kasahara, Yasuhiro Murase, Kohji Matsunaga, Katsumi Yamanoguchi, Hidenori Shimawaki
  • Publication number: 20100224910
    Abstract: Disclosed is an HJFET 110 which comprises: a channel layer 12 composed of InyGa1-yN (0?y?1); a carrier supply layer 13 composed of AlxGa1-xN (0?x?1), the carrier supply layer 13 being provided over the channel layer 12 and including at least one p-type layer; and a source electrode 15S, a drain electrode 15D and a gate electrode 17 which are disposed facing the channel layer 12 through the p-type layer, and provided over the carrier supply layer 13. The following relational expression is satisfied: 5.6×1011x<NA×?×t [cm?2]<5.6×1013x, where x denotes an Al compositional ratio of the carrier supply layer, t denotes a thickness of the p-type layer, NA denotes an impurity concentration, and ? denotes an activation ratio.
    Type: Application
    Filed: March 29, 2007
    Publication date: September 9, 2010
    Applicant: NEC Corporation
    Inventors: Yuji Ando, Hironobu Miyamoto, Tatsuo Nakayama, Yasuhiro Okamoto, Takashi Inoue, Yasuhiro Murase, Kazuki Ota, Akio Wakejima, Naotaka Kuroda
  • Publication number: 20100007013
    Abstract: A semiconductor device, comprising: a semiconductor element 20 having a rectangular two-dimensional geometry and serving as a heat source; and a heat sink section 25 having the semiconductor element 20 mounted thereon, wherein a relation among the directional components of said thermal conductivity is: Kzz?Kyy>Kxx, where directional components of three-dimensional thermal conductivity of the heat sink section 25 in X, Y and Z directions are determined as Kxx, Kyy and Kzz, and where the longer side direction of the semiconductor element 20 is defined as X direction, the shorter side direction thereof is defined as Y direction and the thickness direction is defined as Z direction.
    Type: Application
    Filed: October 25, 2007
    Publication date: January 14, 2010
    Inventors: Naotaka Kuroda, Akio Wakejima, Masahiro Tanomura, Hironobu Miyamoto
  • Publication number: 20090230429
    Abstract: A field effect transistor (100) exhibiting good performance at high voltage operation and high frequency includes a first field plate electrode (116) and a second field plate electrode (118). The second field plate electrode includes a shielding part (119) located in the region between the first field plate electrode and a drain electrode (114), and serves to shield the first field plate electrode from the drain electrode. When in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region where the second field plate electrode (118) overlap the upper part of a structure including the first field plate electrode and a gate electrode (113) is designated as Lol, and the gate length is Lg, the relation expressed as 0?Lol/Lg?1 holds.
    Type: Application
    Filed: June 12, 2006
    Publication date: September 17, 2009
    Applicant: NEC CORPORATION
    Inventors: Hironobu Miyamoto, Yuji Ando, Yasuhiro Okamoto, Tasuo Nakayama, Takashi Inoue, Kazuki Ota, Akio Wakejima, Kensuke Kasahara, Yasuhiro Murase, Kohji Matsunaga, Katsumi Yamanoguchi, Hidenori Shimawaki
  • Publication number: 20090173968
    Abstract: A semiconductor device 100 contains an undoped GaN channel layer 105, an AlGaN electron donor layer 106 provided on the undoped GaN channel layer 105 as being brought into contact therewith, an undoped GaN layer 107 provided on the AlGaN electron donor layer 106, a source electrode 101 and a drain electrode 103 provided on the undoped GaN layer 107 as being spaced from each other, a recess 111 provided in the region between the source electrode 101 and the drain electrode 103, as being extended through the undoped GaN layer 107, a gate electrode 102 buried in the recess 111 as being brought into contact with the AlGaN electron donor layer 106 on the bottom surface thereof, and an SiN film 108 provided on the undoped GaN layer 107, in the region between the gate electrode 102 and the drain electrode 103.
    Type: Application
    Filed: December 12, 2006
    Publication date: July 9, 2009
    Applicant: NEC CORPORATION
    Inventors: Kouji Matsunaga, Kazuki Ota, Yasuhiro Okamoto, Tatsuo Nakayama, Akio Wakejima, Yuji Ando, Hironobu Miyamoto, Takashi Inoue, Yasuhiro Murase
  • Publication number: 20090045438
    Abstract: In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer).
    Type: Application
    Filed: October 25, 2006
    Publication date: February 19, 2009
    Inventors: Takashi Inoue, Tatsuo Nakayama, Yuji Ando, Yasuhiro Murase, Kazuki Ota, Hironobu Miyamoto, Katsumi Yamanoguchi, Naotaka Kuroda, Akio Wakejima, Yasuhiro Okamoto
  • Publication number: 20020171096
    Abstract: In a field effect transistor, there are provided a gate electrode on a Schottky layer over an InP channel layer over the substrate, and a field control electrode extending over an insulating layer and separated from the Schottky layer and being positioned between the gate electrode and the drain electrode for controlling an expansion of a space charge region in the channel layer.
    Type: Application
    Filed: May 17, 2002
    Publication date: November 21, 2002
    Applicant: NEC CORPORATION
    Inventors: Akio Wakejima, Kazuki Ota, Kohji Matsunaga, Walter Contrata, Masaaki Kuzuhara