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Method of making a field effect trench transistor having lightly doped epitaxial region on the surface portion thereof

  • US 5,532,179 A
  • Filed: 05/23/1995
  • Issued: 07/02/1996
  • Est. Priority Date: 07/24/1992
  • Status: Expired due to Term
First Claim
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1. A method of making a field effect transistor comprising the steps of:

  • providing a substrate of a first conductivity type and having a principal surface;

    growing a first epitaxial layer of the first conductivity type on the principal surface, the first epitaxial layer having a doping level less than that of the substrate;

    growing a second epitaxial layer of the first conductivity type on the first epitaxial layer, the second epitaxial layer having a doping level less than that of the first epitaxial layer;

    forming a body region of a second conductivity type in the second epitaxial layer and extending to a principal surface thereof, the body region extending at least partly into the first epitaxial layer;

    forming a source region of the second conductivity type in the body region and extending to the principal surface thereof;

    forming a trench extending from the principal surface of the second epitaxial layer through the source region and the body region, but not extending into the first epitaxial layer; and

    filling the trench at least partially with a conductive gate electrode material.

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