Patents by Inventor Yoshitaka Sasago

Yoshitaka Sasago 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: 20060001081
    Abstract: A leakage current flowing between data lines of a nonvolatile semiconductor memory is reduced. In a memory array of a nonvolatile semiconductor memory device having an AND type flash memory, a concave portion is formed in a junction isolation area between adjacent word limes and between adjacent assist gate wirings AGL, and the height of a main surface (first main surface) of a semiconductor substrate in the region where the concave portion is formed is made lower than that of the main surface (second main surface) of the semiconductor substrate to which an assist gate wiring is facing. As a result, it is possible to control the leakage current that flows between the drain line and source line in the aforementioned junction isolation region during operation of a flash memory.
    Type: Application
    Filed: June 27, 2005
    Publication date: January 5, 2006
    Inventors: Yoshitaka Sasago, Takashi Kobayashi, Naohiro Hosoda, Tetsuo Adachi, Masataka Kato
  • Publication number: 20050212034
    Abstract: A technology realizing decreases of capacitance between the adjoining floating gates and of the threshold voltage shift caused by interference between the adjoining memory cells in a nonvolatile semiconductor memory device with the advances of miniaturization in the period following the 90 nm generation. By having the floating gate 3 of a memory cell with an inverse T-shape and the dimension of a part of the floating gate through the control gate 4 and the second insulator film 8 being smaller than the bottom part of the floating gate, the effects of a threshold voltage shift is reduced maintaining the adequate area of the gap between the floating gate 3 and the control gate 4, decreasing the opposing area of the gap of the floating gates 3 underneath the adjoining word lines WL, maintaining the capacity coupling ratio between the floating gate 3 and the control gate, and reducing the opposing area of the gap of the adjoining floating gates 3.
    Type: Application
    Filed: January 10, 2005
    Publication date: September 29, 2005
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20050173751
    Abstract: A nonvolatile semiconductor memory device that uses inversion layers formed on a surface of its semiconductor substrate as data lines, which is capable of satisfying the requirements of suppressing both characteristic variation among memory cells and bit cost. In order to achieve the above object, in the memory device, a plurality of assist gates are formed so as to be embedded in a p-type well via a silicon oxide film, respectively and silicon nanocrystal grains of about 6 nm in average diameter used for storing information are formed without being in contact with one another. Then, a plurality of word lines are formed practically in a direction vertically to the assist gates and the space between adjacent those of the plurality of word lines is set under ½ of the width (gate length) of the word lines.
    Type: Application
    Filed: December 3, 2004
    Publication date: August 11, 2005
    Inventors: Tomoyuki Ishii, Toshiyuki Mine, Yoshitaka Sasago, Taro Osabe
  • Patent number: 6927443
    Abstract: A nonvolatile semiconductor memory device improved with integration degree, in which the gate of the selection transistors is separated on each of active regions, first and second selection transistors are arranged in two stages in the direction of the global bit line, the gates for the selection transistors in each stage are disposed on every other active regions, contact holes are formed in mirror asymmetry with respect to line B—B in the connection portion for the active regions, the gate is connected through the contact hole to the wiring, the adjacent active regions are connected entirely in one selection transistor portion and connected in an H-shape for adjacent two active regions in another selection transistor portion, and the contact hole is formed in the connection portion and connected when the global bit line, whereby the pitch for the selection transistor portion can be decreased in the direction of the global bit line.
    Type: Grant
    Filed: October 10, 2003
    Date of Patent: August 9, 2005
    Assignee: Renesas Technology Corp.
    Inventors: Tsuyoshi Arigane, Takashi Kobayashi, Yoshitaka Sasago
  • Publication number: 20050151168
    Abstract: Reliability of a semiconductor device having a nonvolatile memory comprising first through third gate electrodes is enhanced. With a flash memory having first gate electrodes (floating gate electrodes), second gate electrodes (control gate electrodes) and third gate electrodes, isolation parts are formed in a self-aligned manner against patterns of a conductor film for forming the third gate electrodes by filling up the respective isolation grooves and a gate insulator film for select nMISes in a peripheral circuit region is formed prior to the formation of the isolation parts. By so doing, deficiency with the gate insulator film for the select nMISes, caused by stress occurring to the isolation parts, can be reduced. Further, with the semiconductor device including the case of stacked memory cells, the patterns of the conductor film for forming the third gate electrodes, serving as a mask for forming the isolation parts in the self-aligned manner, can be formed without misalignment against channels.
    Type: Application
    Filed: December 28, 2004
    Publication date: July 14, 2005
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20050127429
    Abstract: A low cost semiconductor nonvolatile memory device capable of high speed programming, using an inversion layer as the wiring, and a manufacturing method for that device. The semiconductor memory device includes an auxiliary electrode at a position between and in parallel with the source and drain regions and with no position overlap versus the source region and the drain region formed mutually in parallel; wherein the auxiliary electrode for hot electron source injection is utilized as the auxiliary electrode for programming (writing); and an inversion layer formed below the auxiliary electrode is utilized as the source region or as the drain region during the read operation.
    Type: Application
    Filed: November 30, 2004
    Publication date: June 16, 2005
    Inventors: Kazuo Otsuga, Hideaki Kurata, Yoshitaka Sasago
  • Publication number: 20050062096
    Abstract: A nonvolatile semiconductor memory device, in which an inversion layer formed over a semiconductor substrate is used as a data line, is achieved with its high integration and high performance. A memory cell is composed of a MOS transistor having a floating gate, a control gate constituting a word line, and a buried gate. The buried gate is buried in a groove formed in a self-alignment manner with respect to the floating gate. The buried gate and the control gate disposed over it are isolated from each other by a thick silicon oxide film on the groove and a second gate insulator film formed thereon. A source and drain of the memory cell are composed of an inversion layer (local data line) formed on a p type well disposed below the buried gate when a positive voltage is applied to the buried gate.
    Type: Application
    Filed: July 20, 2004
    Publication date: March 24, 2005
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Patent number: 6849502
    Abstract: Reliability of a semiconductor device having a nonvolatile memory comprising first through third gate electrodes is enhanced. With a flash memory having first gate electrodes (floating gate electrodes), second gate electrodes (control gate electrodes) and third gate electrodes, isolation parts are formed in a self-aligned manner against patterns of a conductor film for forming the third gate electrodes by filling up the respective isolation grooves and a gate insulator film for select nMISes in a peripheral circuit region is formed prior to the formation of the isolation parts. By so doing, deficiency with the gate insulator film for the select nMISes, caused by stress occurring to the isolation parts, can be reduced. Further, with the semiconductor device including the case of stacked memory cells, the patterns of the conductor film for forming the third gate electrodes, serving as a mask for forming the isolation parts in the self-aligned manner, can be formed without misalignment against channels.
    Type: Grant
    Filed: June 10, 2003
    Date of Patent: February 1, 2005
    Assignee: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20040129986
    Abstract: The object of the present invention is to provide a new nonvolatile semiconductor memory device and its manufacturing method for the purpose of miniaturizing a virtual grounding type memory cell based on a three-layer polysilicon gate, enhancing the performance, and boosting the yield. In a memory cell according to the present invention, a floating gate's two end faces perpendicular to a word line and channel are partly placed over the top of a third gate via a dielectric film. The present invention can reduce the memory cell area of a nonvolatile semiconductor memory device, increase the operating speed, and enhances the yield.
    Type: Application
    Filed: November 24, 2003
    Publication date: July 8, 2004
    Applicant: Renesas Technology Corp.
    Inventors: Takashi Kobayashi, Yoshitaka Sasago, Tsuyoshi Arigane, Yoshihiro Ikeda, Kenji Kanamitsu
  • Publication number: 20040124459
    Abstract: The present invention enables to avoid a reduction in coupling ratio in a nonvolatile semiconductor memory device. The reduction is coupling ratio is caused due to difficulties in batch forming of a control gate material, an interpoly dielectric film material, and a floating gate material, the difficulties accompanying a reduction in word line width. Further, the invention enables to avoid damage caused in the batch forming on a gate oxide film. Before forming floating gates of memory cells of a nonvolatile memory, a space enclosed by insulating layers is formed for each of the floating gates of the memory cells, so that the floating gate is buried in the space. This structure is realized by processing the floating gates in a self alignment manner after depositing the floating gate material.
    Type: Application
    Filed: April 17, 2003
    Publication date: July 1, 2004
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20040102008
    Abstract: In a channel region between the source/drain diffusion layers, impurities of the same conductivity type as the well are doped in an area apart from the diffusion regions. By using as a mask the gate formed in advance, tilted ion implantation in opposite directions is performed to form the diffusion layers and heavily impurity doped region of the same conductivity type as the well in a self-alignment manner relative to the gate.
    Type: Application
    Filed: November 6, 2003
    Publication date: May 27, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20040076072
    Abstract: A nonvolatile semiconductor memory device improved with integration degree, in which the gate of the selection transistors is separated on each of active regions, first and second selection transistors are arranged in two stages in the direction of the global bit line, the gates for the selection transistors in each stage are disposed on every other active regions, contact holes are formed in mirror asymmetry with respect to line B-B in the connection portion for the active regions, the gate is connected through the contact hole to the wiring, the adjacent active regions are connected entirely in one selection transistor portion and connected in an H-shape for adjacent two active regions in another selection transistor portion, and the contact hole is formed in the connection -portion and connected when the global bit line, whereby the pitch for the selection transistor portion can be decreased in the direction of the global bit line.
    Type: Application
    Filed: October 10, 2003
    Publication date: April 22, 2004
    Applicant: Renesas Technology Corp.
    Inventors: Tsuyoshi Arigane, Takashi Kobayashi, Yoshitaka Sasago
  • Patent number: 6670671
    Abstract: In a channel region between the source/drain diffusion layers, impurities of the same conductivity type as the well are doped in an area apart from the diffusion regions. By using as a mask the gate formed in advance, tilted ion implantation in opposite directions is performed to form the diffusion layers and heavily impurity doped region of the same conductivity type as the well in a self-alignment manner relative to the gate.
    Type: Grant
    Filed: June 11, 2002
    Date of Patent: December 30, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20030235953
    Abstract: Reliability of a semiconductor device having a nonvolatile memory comprising first through third gate electrodes is enhanced. With a flash memory having first gate electrodes (floating gate electrodes), second gate electrodes (control gate electrodes) and third gate electrodes, isolation parts are formed in a self-aligned manner against patterns of a conductor film for forming the third gate electrodes by filling up the respective isolation grooves and a gate insulator film for select nMISes in a peripheral circuit region is formed prior to the formation of the isolation parts. By so doing, deficiency with the gate insulator film for the select nMISes, caused by stress occurring to the isolation parts, can be reduced. Further, with the semiconductor device including the case of stacked memory cells, the patterns of the conductor film for forming the third gate electrodes, serving as a mask for forming the isolation parts in the self-aligned manner, can be formed without misalignment against channels.
    Type: Application
    Filed: June 10, 2003
    Publication date: December 25, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Takashi Kobayashi
  • Publication number: 20020190306
    Abstract: In a channel region between the source/drain diffusion layers, impurities of the same conductivity type as the well are doped in an area apart from the diffusion regions. By using as a mask the gate formed in advance, tilted ion implantation in opposite directions is performed to form the diffusion layers and heavily impurity doped region of the same conductivity type as the well in a self-alignment manner relative to the gate.
    Type: Application
    Filed: June 11, 2002
    Publication date: December 19, 2002
    Applicant: Hitachi, Ltd.
    Inventors: Yoshitaka Sasago, Takashi Kobayashi