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Bidirectional trench gated power mosfet with submerged body bus extending underneath gate trench

  • US 6,096,608 A
  • Filed: 11/03/1998
  • Issued: 08/01/2000
  • Est. Priority Date: 06/30/1997
  • Status: Expired due to Term
First Claim
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1. A method of forming a trench power MOSFET comprising:

  • providing a semiconductor substrate of a first conductivity type;

    growing an epitaxial layer of the first conductivity type on the substrate;

    forming a first mask layer on a surface of the epitaxial layer, the first mask layer having a first opening;

    implanting dopant of a second conductivity type opposite to the first conductivity type through the first opening to form a deep diffusion of the second conductivity type in the epitaxial layer;

    removing the first mask layer;

    forming a second mask layer on the surface of the epitaxial layer, the second mask layer having a second opening;

    etching the epitaxial layer through the second opening to form a trench in the epitaxial layer;

    forming a first insulating layer on a wall of the trench;

    introducing a conductive gate material into the trench;

    implanting dopant of the second conductivity type to form a body region adjacent the trench;

    implanting dopant of the first conductivity type in a first area of the surface of the epitaxial layer to form a source region adjacent the trench and the surface of the epitaxial layer;

    implanting dopant of the second conductivity type in a second area of the surface of the epitaxial layer to form a body contact region adjacent the second area of the surface of the epitaxial layer, the body contact region adjoining and being more heavily doped than the body region, the second area occupied by the body contact region at the surface of the epitaxial layer being spaced apart from the first area occupied by the source region at the surface of the epitaxial layer;

    forming a second insulating layer over the surface of the epitaxial layer;

    forming first, second and third contact openings through the second insulating layer, the first contact opening exposing a portion of the source region, the second contact opening exposing a portion of the body contact region, and the third contact opening exposing a portion of the deep diffusion;

    depositing a metal layer, the metal layer making electrical contact with the source region, body contact region and deep diffusion through the first, second and third contact openings, respectively; and

    separating the metal layer into a source contact bus and a body contact bus, the source contact bus including a portion of the metal layer which extends into the first opening and the body contact bus including a portion of the metal layer which extends into the second and third openings.

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