Patents by Inventor Natsuki Yokoyama

Natsuki Yokoyama 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: 20110220916
    Abstract: A normally-off type silicon carbide junction FET has a problem that the gate thereof is not easy to use due to inferiority in the characteristics of it. This problem occurs because in order to achieve normally-off, the gate voltage should be off at 0V and at the same time, the ON-state gate voltage should be suppressed to about 2.5V to prevent the passage of an electric current through a pn junction between gate and source. Accordingly, a range from the threshold voltage to the ON-state gate voltage is only from about 1 V to 2V and it is difficult to control the gate voltage. Provided in the present invention is an electronic circuit device obtained by coupling, to a gate of a normally-off type silicon carbide junction FET, an element having a capacitance equal to or a little smaller than the gate capacitance of the junction FET.
    Type: Application
    Filed: March 8, 2011
    Publication date: September 15, 2011
    Applicant: RENESAS ELECTRONICS CORPORATION
    Inventors: Haruka SHIMIZU, Natsuki YOKOYAMA
  • Publication number: 20110198613
    Abstract: The leakage current generated in a pn junction region between a gate and a source is reduced in a junction FET using a silicon carbide substrate. In a trench junction FET using a silicon carbide substrate, nitrogen is introduced into a sidewall and a bottom surface of a trench, thereby forming an n type layer and an n+ type layer on a surface of the trench. In this manner, the pn junction region corresponding to the junction region between a p+ type gate region and an n+ type source region is exposed on a main surface of a semiconductor substrate instead of on the damaged sidewall of the trench, and also the exposed region thereof is narrowed. Accordingly, the leakage current in the pn junction region can be reduced.
    Type: Application
    Filed: February 3, 2011
    Publication date: August 18, 2011
    Applicant: RENESAS ELECTRONICS CORPORATION
    Inventors: Haruka SHIMIZU, Natsuki YOKOYAMA
  • Patent number: 7906796
    Abstract: In a bipolar device, such as transistor or a thyristor, the emitter layer or the anode layer is formed of two high-doped and low-doped layers, a semiconductor region for suppressing recombination comprising an identical semiconductor having an impurity density identical with that of the low-doped layer is present being in contact with a base layer or a gate layer and a surface passivation layer, and the width of the semiconductor region for suppressing recombination is defined equal with or longer than the diffusion length of the carrier. This provides, among other things, an effect of attaining reduction in the size of the bipolar transistor or improvement of the switching frequency of the thyristor without deteriorating the performance.
    Type: Grant
    Filed: July 21, 2008
    Date of Patent: March 15, 2011
    Assignee: Hitachi, Ltd.
    Inventors: Kazuhiro Mochizuki, Hidekatsu Onose, Natsuki Yokoyama
  • Publication number: 20110018004
    Abstract: There is no effective method for fabricating a semiconductor power device containing UMOSFET possessing large channel mobility and whose threshold voltage can be lowered with no loss in blocking voltage. A semiconductor device with large blocking voltage is provided utilizing silicon carbide trench MOSFET possessing both narrow regions where the p body concentration is low, and wide regions where the p body concentration is high.
    Type: Application
    Filed: July 12, 2010
    Publication date: January 27, 2011
    Inventors: Haruka SHIMIZU, Natsuki Yokoyama
  • Patent number: 7772613
    Abstract: A normally-off type junction FET in which a channel resistance is reduced without lowering its blocking voltage is provided. In a junction FET formed with using a substrate made of silicon carbide, an impurity concentration of a channel region (second epitaxial layer) is made higher than an impurity concentration of a first epitaxial layer to be a drift layer. The channel region is formed of a first region in which a channel width is constant and a second region below the first region in which the channel width becomes wider toward the drain (substrate) side. A boundary between the first epitaxial layer and the second epitaxial layer is positioned in the second region in which the channel width becomes wider toward the drain (substrate) side.
    Type: Grant
    Filed: July 31, 2009
    Date of Patent: August 10, 2010
    Assignee: Renesas Technology Corp.
    Inventors: Haruka Shimizu, Natsuki Yokoyama
  • Publication number: 20100163935
    Abstract: In a junction FET of a normally-off type, a technique capable of achieving both of improvement of a blocking voltage and reduction of an ON resistance is provided. In a junction FET using silicon carbide as a substrate material, impurities are doped to a vicinity of a p-n junction between a gate region and a channel-formed region, the impurities having a conductive type which is reverse to that of impurities doped in the gate region and same as that of impurities doped in the channel-formed region. In this manner, an impurity profile of the p-n junction becomes abrupt, and further, an impurity concentration of a junction region forming the p-n junction with the gate region in the channel-formed region is higher than those of a center region in the channel-formed region and of an epitaxial layer.
    Type: Application
    Filed: December 16, 2009
    Publication date: July 1, 2010
    Inventors: Haruka Shimizu, Natsuki Yokoyama
  • Publication number: 20100131093
    Abstract: A fabricating method for a system that includes a plurality of processing apparatuses connected to each other by an inter-apparatus transporter and a computer storing managing information of processing and transporting of semiconductor wafers. The processing apparatuses have an interface for loading and unloading a plurality of the semiconductor wafers that are contained in a carrier. The semiconductor waters are processed in processing chambers of the processing apparatuses and the result of processing is monitored. In the processing, a first carrier containing the plurality of the semiconductor wafers having been processed in the first processing apparatus is transported toward the second processing apparatus by the inter-apparatus transporter prior to unloading of a second carrier containing semiconductor wafers processed in the second processing apparatus, according to the managing information.
    Type: Application
    Filed: September 9, 2009
    Publication date: May 27, 2010
    Applicant: RENESAS TECHNOLOGY CORP.
    Inventors: Natsuki YOKOYAMA, Yoshifumi KAWAMOTO, Eiichi MURAKAMI, Fumihiko UCHIDA, Kenichi MIZUISHI, Yoshio KAWAMURA
  • Patent number: 7682990
    Abstract: Conventionally, a MONOS type nonvolatile memory is fabricated by subjecting a silicon nitride film to ISSG oxidation to form a top silicon oxide film of ONO structure. If the ISSG oxidation conditions are severe, repeats of programming/erase operation cause increase of interface state density (Dit) and electron trap density. This does not provide a sufficient value of the on current, posing a problem in that the deterioration of charge trapping properties cannot be suppressed. For the solution to the problem, the silicon nitride film is oxidized by means of a high concentration ozone gas to form the top silicon oxide film.
    Type: Grant
    Filed: June 6, 2005
    Date of Patent: March 23, 2010
    Assignee: Renesas Technology Corp.
    Inventors: Hirotaka Hamamura, Toshiyuki Mine, Natsuki Yokoyama
  • Publication number: 20100025739
    Abstract: A normally-off type junction FET in which a channel resistance is reduced without lowering its blocking voltage is provided. In a junction FET formed with using a substrate made of silicon carbide, an impurity concentration of a channel region (second epitaxial layer) is made higher than an impurity concentration of a first epitaxial layer to be a drift layer. The channel region is formed of a first region in which a channel width is constant and a second region below the first region in which the channel width becomes wider toward the drain (substrate) side. A boundary between the first epitaxial layer and the second epitaxial layer is positioned in the second region in which the channel width becomes wider toward the drain (substrate) side.
    Type: Application
    Filed: July 31, 2009
    Publication date: February 4, 2010
    Applicant: RENESAS TECHNOLOGY CORP.
    Inventors: Haruka SHIMIZU, Natsuki YOKOYAMA
  • Publication number: 20090302328
    Abstract: A buffer layer configured of the same conductive semiconductor layers of two or more layers as a drift layer is installed by epitaxial growth between a first semiconductor layer configuring the drift layer that is a layer in which components of the semiconductor device are made and a base substrate including a silicon carbide single crystal wafer. A step of donor concentration is provided at an interface between the drift layer and the buffer layer, an interface between the semiconductor layers configuring the buffer layer, and an interface between the buffer layer and the base substrate and the donor concentration of the drift layer side is lower than that of the base substrate side, thereby making it possible to convert most basal plane dislocations into threading edge dislocations as compared to the drift layer having one layer or the buffer layer configured of one layer.
    Type: Application
    Filed: May 28, 2009
    Publication date: December 10, 2009
    Inventors: Toshiyuki Ohno, Natsuki Yokoyama, Hajime Goto
  • Patent number: 7603194
    Abstract: A fabricating method for a system that includes a plurality of processing apparatuses connected to each other by an inter-apparatus transporter and a computer storing managing information of processing and transporting of semiconductor wafers. The processing apparatuses have an interface for loading and unloading a plurality of the semiconductor wafers that are contained in a carrier. The semiconductor waters are processed in processing chambers of the processing apparatuses and the result of processing is monitored. In the processing, a first carrier containing the plurality of the semiconductor wafers having been processed in the first processing apparatus is transported toward the second processing apparatus by the inter-apparatus transporter prior to unloading of a second carrier containing semiconductor wafers processed in the second processing apparatus, according to the managing information.
    Type: Grant
    Filed: May 28, 2008
    Date of Patent: October 13, 2009
    Assignee: Renesas Technology Corp.
    Inventors: Natsuki Yokoyama, Yoshifumi Kawamoto, Eiichi Murakami, Fumihiko Uchida, Kenichi Mizuishi, Yoshio Kawamura
  • Publication number: 20090209090
    Abstract: A problem in the conventional technique is that metal contamination on a silicon carbide surface is not sufficiently removed in a manufacturing method of a semiconductor device using a monocrystalline silicon carbide substrate. Accordingly, there is a high possibility that the initial characteristics of a manufactured silicon carbide semiconductor device are deteriorated and the yield rate is decreased. Further, it is conceivable that the metal contamination has an adverse affect even on the long-term reliability of a semiconductor device. In a manufacturing method of a semiconductor device using a monocrystalline silicon carbide substrate, there is applied a metal contamination removal process, on a silicon carbide surface, including a step of oxidizing the silicon carbide surface and a step of removing a film primarily including silicon dioxide formed on the silicon carbide surface by the step.
    Type: Application
    Filed: November 11, 2008
    Publication date: August 20, 2009
    Inventors: Natsuki YOKOYAMA, Tomoyuki SOMEYA
  • Publication number: 20090085044
    Abstract: A manufacturing method is provided for a silicon carbide semiconductor substrate adapted for reduced basal plane dislocations in a silicon carbide epitaxial layer. Between a silicon carbide epitaxial layer for device fabrication (i.e., a drift layer) and a base substrate formed of a silicon carbide single-crystal wafer, a highly efficient dislocation conversion layer through which any basal plane dislocations in the silicon carbide single-crystal wafer are converted into threading edge dislocations very efficiently when the dislocations propagate into the layer epitaxially grown is provided by epitaxial growth. Assigning to the dislocation conversion layer a donor concentration lower than that of the drift layer, therefore, allows the above conversion of a larger number of basal plane dislocations than the case where the drift layer exists alone (without the dislocation conversion layer).
    Type: Application
    Filed: August 20, 2008
    Publication date: April 2, 2009
    Inventors: Toshiyuki Ohno, Natsuki Yokoyama
  • Publication number: 20090064785
    Abstract: In the manufacturing technology of an integrated MEMS in which a semiconductor integrated circuit (CMOS or the like) and a micro machine are monolithically integrated on a semiconductor substrate, a technology capable of manufacturing the integrated MEMS without using a special process different from the normal manufacturing technology of a semiconductor integrated circuit is provided. A MEMS structure is formed together with an integrated circuit by using the CMOS integrated circuit process. For example, when forming an acceleration sensor, a structure composed of a movable mass, an elastic beam and a fixed beam is formed by using the CMOS interconnect technology. Thereafter, an interlayer dielectric and the like are etched by using the CMOS process to form a cavity. Then, fine holes used in the etching are sealed with a dielectric.
    Type: Application
    Filed: July 2, 2008
    Publication date: March 12, 2009
    Inventors: Hiroshi Fukuda, Tsukasa Fujimori, Natsuki Yokoyama, Yuko Hanaoka, Takafumi Matsumura
  • Publication number: 20090057685
    Abstract: In a mesa type bipolar transistor or a thyristor, since carriers injected from an emitter layer or an anode layer to a base layer or a gate layer diffuse laterally and are recombined, reduction in the size and improvement for the switching frequency is difficult. In the invention, the emitter layer or the anode layer is formed of two high-doped and low-doped layers, a semiconductor region for suppressing recombination comprising an identical semiconductor having an impurity density identical with that of the low-doped layer is present being in contact with a base layer or a gate layer and a surface passivation layer, and the width of the semiconductor region for suppressing recombination is defined equal with or longer than the diffusion length of the carrier. This provides an effect of attaining reduction in the size of the bipolar transistor or improvement of the switching frequency of the thyristor without deteriorating the performance.
    Type: Application
    Filed: July 21, 2008
    Publication date: March 5, 2009
    Inventors: Kazuhiro MOCHIZUKI, Hidekatsu Onose, Natsuki Yokoyama
  • Patent number: 7451656
    Abstract: The method for promoting the size reduction, the performance improvement and the reliability improvement of a semiconductor device embedded with pressure sensor is provided. In a semiconductor device embedded with pressure sensor, a part of an uppermost wiring is used as a lower electrode of a pressure detecting unit. A part of a silicon oxide film formed on the lower electrode is a cavity. On a tungsten silicide film formed on the silicon oxide film, a silicon nitride film is formed. The silicon nitride film has a function to fill a hole or holes and suppress immersion of moisture from outside to the semiconductor device embedded with pressure sensor. A laminated film of the silicon nitride film and the tungsten silicide film forms a diaphragm of the pressure sensor.
    Type: Grant
    Filed: July 23, 2007
    Date of Patent: November 18, 2008
    Assignee: Hitachi, Ltd.
    Inventors: Natsuki Yokoyama, Shuntaro Machida, Yasushi Goto
  • Publication number: 20080243293
    Abstract: A fabricating method for a system that includes a plurality of processing apparatuses connected to each other by an inter-apparatus transporter and a computer storing managing information of processing and transporting of semiconductor wafers. The processing apparatuses have an interface for loading and unloading a plurality of the semiconductor wafers that are contained in a carrier. The semiconductor waters are processed in processing chambers of the processing apparatuses and the result of processing is monitored. In the processing, a first carrier containing the plurality of the semiconductor wafers having been processed in the first processing apparatus is transported toward the second processing apparatus by the inter-apparatus transporter prior to unloading of a second carrier containing semiconductor wafers processed in the second processing apparatus, according to the managing information.
    Type: Application
    Filed: May 28, 2008
    Publication date: October 2, 2008
    Inventors: Natsuki Yokoyama, Yoshifumi Kawamoto, Eiichi Murakami, Fumihiko Uchida, Kenichi Mizuishi, Yoshio Kawamura
  • Patent number: 7405588
    Abstract: The present invention relates to an LSI in which functions can be changed, and realizes, particularly, a system LSI in which functions are changed by changing connections of the circuit by use of MEMS switches. A bistable MEMS switch which can maintain states, and exhibits optimal stitching property, i.e., the switch has a very small resistance of several ? or less in an on-state, and has an infinite resistance in an off-state; is employed. An element in which functions can be changed during operation, is produced by utilizing a wiring layer of a CMOS semiconductor to form the MEMS switch. A semiconductor device exhibiting high-degree of freedom for changing functions, high-speed, and having small area, is realized.
    Type: Grant
    Filed: September 3, 2004
    Date of Patent: July 29, 2008
    Assignee: Hitachi, Ltd.
    Inventors: Takayuki Kawahara, Masayuki Miyazaki, Yasushi Goto, Natsuki Yokoyama, Takahiro Onai
  • Patent number: 7402449
    Abstract: In the manufacturing technology of an integrated MEMS in which a semiconductor integrated circuit (CMOS or the like) and a micro machine are monolithically integrated on a semiconductor substrate, a technology capable of manufacturing the integrated MEMS without using a special process different from the normal manufacturing technology of a semiconductor integrated circuit is provided. A MEMS structure is formed together with an integrated circuit by using the CMOS integrated circuit process. For example, when forming an acceleration sensor, a structure composed of a movable mass, an elastic beam and a fixed beam is formed by using the CMOS interconnect technology. Thereafter, an interlayer dielectric and the like are etched by using the CMOS process to form a cavity. Then, fine holes used in the etching are sealed with a dielectric.
    Type: Grant
    Filed: August 23, 2005
    Date of Patent: July 22, 2008
    Assignee: Hitachi, Ltd.
    Inventors: Hiroshi Fukuda, Tsukasa Fujimori, Natsuki Yokoyama, Yuko Hanaoka, Takafumi Matsumura
  • Patent number: 7392106
    Abstract: A fabricating method for a system that includes a plurality of processing apparatuses connected to each other by an inter-apparatus transporter and a computer storing managing information of processing and transporting of semiconductor wafers. The processing apparatuses have an interface for loading and unloading a plurality of the semiconductor wafers that are contained in a carrier. The semiconductor waters are processed in processing chambers of the processing apparatuses and the result of processing is monitored. In the processing, a first carrier containing the plurality of the semiconductor wafers having been processed in the first processing apparatus is transported toward the second processing apparatus by the inter-apparatus transporter prior to unloading of a second carrier containing semiconductor wafers processed in the second processing apparatus, according to the managing information.
    Type: Grant
    Filed: December 30, 2005
    Date of Patent: June 24, 2008
    Assignee: Renesas Technology Corp.
    Inventors: Natsuki Yokoyama, Yoshifumi Kawamoto, Eiichi Murakami, Fumihiko Uchida, Kenichi Mizuishi, Yoshio Kawamura