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Vertical power MOSFET having reduced sensitivity to variations in thickness of epitaxial layer

  • US 5,814,858 A
  • Filed: 03/15/1996
  • Issued: 09/29/1998
  • Est. Priority Date: 03/15/1996
  • Status: Expired due to Term
First Claim
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1. A vertical trench-gated power MOSFET comprising:

  • a semiconductor substrate of a first conductivity type;

    an epitaxial layer formed on said substrate;

    a gate formed in a trench extending downward from a surface of said epitaxial layer;

    a source region of said first conductivity type formed in said epitaxial layer adjacent said surface thereof;

    a body region of a second conductivity type opposite to said first conductivity type formed in said epitaxial layer adjacent said source region and a wall of said trench, said source and body regions being formed in a cell of said MOSFET bordered on at least two sides by said trench;

    a drain which comprises said substrate and a portion of said epitaxial layer located adjacent said body region, said portion of said epitaxial layer being doped with ions of said first conductivity type to a first concentration level; and

    a buried layer formed within said epitaxial layer and extending continuously across said cell, said buried layer having an upper edge that is located at a level above an interface between said substrate and said epitaxial layer and a lower edge that is located at a level below said interface, a portion of said buried layer within said epitaxial layer being doped with ions of said first conductivity type to a second concentration level which is greater than said first concentration level.

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