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Method of production of vertical MOS transistor

  • US 5,242,845 A
  • Filed: 04/10/1992
  • Issued: 09/07/1993
  • Est. Priority Date: 06/13/1990
  • Status: Expired due to Term
First Claim
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1. A method of producing a vertical MOS transistor comprising the steps of:

  • (a) forming a first impurity region on the surface of a semiconductor substrate and a second impurity region under the first impurity region such that the conduction type of the second impurity region is opposite to that of the first impurity region;

    (b) engraving a trench on the surface of the semiconductor substrate to cut through the first and second impurity regions deeper than at least the bottom of the second impurity region;

    (c) forming a first insulation film in the trench, disposing conductive material in the trench on the first insulation film, removing a part of the first insulation film to leave a first gate insulation film on the bottom of the trench, the upper end of the first gate insulation film being located lower than the bottom of the second impurity region; and

    (d) forming a second insulation film which is thinner than the first gate insulation film over the first gate electrode in the trench and over the upper side walls of the trench, and disposing conductive material on the second insulation film, thereby forming a second gate insulation film thinner than the first gate insulation film and a second gate electrode.

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