Patents by Inventor Tatsuya Kajita

Tatsuya Kajita 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: 5907781
    Abstract: A method of forming a contact in a flash memory device utilizes a local interconnect process technique. The local interconnect process technique allows the contact to butt against or overlap a stacked gate associated with the memory cell. The contact can include tungsten. The stacked gate is covered by a barrier layer which also covers the insulative spacers.
    Type: Grant
    Filed: March 27, 1998
    Date of Patent: May 25, 1999
    Assignees: Advanced Micro Devices, Inc., Fujitsu Limited, Fujitsu AMD Semiconductor Limited
    Inventors: Hung-Sheng Chen, Unsoon Kim, Yu Sun, Chi Chang, Mark Ramsbey, Mark Randolph, Tatsuya Kajita, Angela Hui, Fei Wang, Mark Chang
  • Patent number: 5870337
    Abstract: A flash-erasable semiconductor memory device has a memory cell array including a plurality of memory cell transistors each having an insulated floating gate for storing information and a control electrode provided on the floating gate, wherein the flash-erasable semiconductor memory device includes a write control circuit supplied with a write control signal, when writing information. The write control circuit produces a control signal such that a leading edge of the drain control signal appears after a leading edge of the gate control signal. Further, the gate control circuit shuts off the gate control signal such that a trailing edge of the gate control signal appears after a trailing edge of the drain control signal.
    Type: Grant
    Filed: December 5, 1997
    Date of Patent: February 9, 1999
    Assignees: Fujitsu Limited, Fujitsu VLSI Limited
    Inventors: Takao Akaogi, Yasushige Ogawa, Tatsuya Kajita, Hisayoshi Watanabe, Minoru Yamashita
  • Patent number: 5835416
    Abstract: A flash-erasable semiconductor memory device comprises a memory cell array including a plurality of memory cell transistors each having an insulated floating gate for storing information and a control electrode provided on said floating gate, wherein the flash-erasable semiconductor memory device includes a write control circuit supplied with a write control signal, when writing information. The write control circuit produces a control signal such that a leading edge of the drain control signal appears after a leading edge of the gate control signal. Further, the gate control circuit shuts off the gate control signal such that a trailing edge of the gate control signal appears after a trailing edge of the drain control signal.
    Type: Grant
    Filed: December 5, 1997
    Date of Patent: November 10, 1998
    Assignees: Fujitsu Limited, Fujitsu VLSI Limited
    Inventors: Takao Akaogi, Yasushige Ogawa, Tatsuya Kajita, Hisayoshi Watanabe, Minoru Yamashita
  • Patent number: 5835408
    Abstract: A flash-erasable semiconductor memory device has a memory cell array including a plurality of memory cell transistors each having an insulated floating gate for storing information and a control electrode provided on the floating gate, wherein the flash-erasable semiconductor memory device includes a write control circuit supplied with a write control signal, when writing information. The write control circuit produces a control signal such that a leading edge of the drain control signal appears after a leading edge of the gate control signal. Further, the gate control circuit shuts off the gate control signal such that a trailing edge of the gate control signal appears after a trailing edge of the drain control signal.
    Type: Grant
    Filed: December 5, 1997
    Date of Patent: November 10, 1998
    Assignees: Fujitsu Limited, Fujitsu VLSI Limited
    Inventors: Takao Akaogi, Yasushige Ogawa, Tatsuya Kajita, Hisayoshi Watanabe, Minoru Yamashita
  • Patent number: 5761127
    Abstract: A flash-erasable semiconductor memory device comprises a memory cell array including a plurality of memory cell transistors each having an insulated floating gate for storing information and a control electrode provided on said floating gate, wherein the flash-erasable semiconductor memory device includes a write control circuit supplied with a write control signal, when writing information. The write control circuit produces a control signal such that a leading edge of the drain control signal appears after a leading edge of the gate control signal. Further, the gate control circuit shuts off the gate control signal such that a trailing edge of the gate control signal appears after a trailing edge of the drain control signal.
    Type: Grant
    Filed: November 20, 1992
    Date of Patent: June 2, 1998
    Assignees: Fujitsu Limited, Fujitsu VLSI Limited
    Inventors: Takao Akaogi, Yasushige Ogawa, Tatsuya Kajita, Hisayoshi Watanabe, Minoru Yamashita
  • Patent number: 5641979
    Abstract: A memory cell includes a transfer transistor having a gate which is connected to a word line, a first electrode which is connected to a bit line, and a second electrode, and a storage capacitor having a storage electrode which is connected to the second electrode of the transfer transistor, a confronting electrode, and a charge storage layer which is provided between the storage electrode and the confronting electrode. The storage capacitor has a capacitance which changes with a hysteresis curve which is determined by a bias voltage applied across the storage electrode and the confronting electrode, so that the capacitance takes one of two values depending on the bias voltage.
    Type: Grant
    Filed: January 3, 1994
    Date of Patent: June 24, 1997
    Assignee: Fujitsu Limited
    Inventors: Taiji Ema, Tatsuya Kajita
  • Patent number: 5497018
    Abstract: A method for fabricating a flash-EPROM comprises the steps of forming a first gate insulation film and a second gate insulation film on a semiconductor substrate so as to respectively cover first and second device regions, providing a first conductor layer so as to cover both the first device region and the second device region, patterning the first conductor layer to form a floating gate electrode in correspondence to the first device region, oxidizing a surface of the first conductor layer to form a capacitor insulation film surrounding the floating gate electrode, providing a second conductor layer on the first conductor layer as to bury underneath the floating gate electrode covered by the capacitor insulation film, patterning the second conductor layer on the first device region to form a control gate electrode, exposing the first conductor layer in correspondence to the second device region, and patterning the first conductor layer remaining on the second element region to form a gate electrode of a per
    Type: Grant
    Filed: August 31, 1994
    Date of Patent: March 5, 1996
    Assignee: Fujitsu Limited
    Inventor: Tatsuya Kajita
  • Patent number: 5468664
    Abstract: A semiconductor device includes a base layer, a chip region formed on the base layer, a peripheral region which surrounds the chip region on the base layer, and a patterned stacked structure formed on the base layer in both the chip region and the peripheral region. The patterned stacked structure includes a lower layer which is formed on the base layer, an intermediate layer which is formed on the lower layer and an upper layer formed on the intermediate layer. The upper layer and the intermediate layer are aligned to one side surface of the lower layer in at least a part of the chip region. The intermediate layer and the upper layer cover one side surface of the lower layer in at least a part of the peripheral region.
    Type: Grant
    Filed: November 16, 1994
    Date of Patent: November 21, 1995
    Assignee: Fujitsu Limited
    Inventor: Tatsuya Kajita
  • Patent number: 5449629
    Abstract: A method for fabricating a flash-EPROM comprises the steps of forming a first gate insulation film and a second gate insulation film on a semiconductor substrate so as to respectively cover first and second device regions, providing a first conductor layer so as to cover both the first device region and the second device region, patterning the first conductor layer to form a floating gate electrode in correspondence to the first device region, oxidizing a surface of the first conductor layer to form a capacitor insulation film surrounding the floating gate electrode, providing a second conductor layer on the first conductor layer as to bury underneath the floating gate electrode covered by the capacitor insulation film, patterning the second conductor layer on the first device region to form a control gate electrode, exposing the first conductor layer in correspondence to the second device region, and patterning the first conductor layer remaining on the second element region to form a gate electrode of a per
    Type: Grant
    Filed: November 13, 1992
    Date of Patent: September 12, 1995
    Assignee: Fujitsu Limited
    Inventor: Tatsuya Kajita
  • Patent number: 5391902
    Abstract: A semiconductor device includes a base layer, a chip region formed on the base layer, a peripheral region which surrounds the chip region on the base layer, and a patterned stacked structure formed on the base layer in both the chip region and the peripheral region, where the patterned stacked structure includes a lower layer which is formed on the base layer, an intermediate layer which is formed on the lower layer and an upper layer formed on the intermediate layer. The upper layer and the intermediate layer are aligned to one side surface of the lower layer in at least a part of the chip region, and the intermediate layer and the upper layer cover one side surface of the lower layer in at least a part of the peripheral region.
    Type: Grant
    Filed: August 24, 1992
    Date of Patent: February 21, 1995
    Assignee: Fujitsu Limited
    Inventor: Tatsuya Kajita