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Low voltage high density trench-gated power device with uniformly doped channel and its edge termination technique

  • US 6,784,505 B2
  • Filed: 05/03/2002
  • Issued: 08/31/2004
  • Est. Priority Date: 05/03/2002
  • Status: Expired due to Term
First Claim
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1. A power mosfet with trench gates comprising:

  • a semiconductor substrate;

    a drain layer on one surface of the substrate doped with a high concentration of a dopant of one polarity;

    an epitaxial layer above the drain layer and lightly doped with a dopant of opposite polarity;

    a source layer at the other surface of the substrate and doped with a high concentration of the same dopant as the drain layer;

    a plurality of trenches penetrating the source layer, said trenches substantially filled with conductive gate polycrystalline material doped with the same dopant type as the source layer; and

    a drift layer in the substrate forming a continuous lightly doped drift region extending between sidewalls of the trenches and from the drain layer toward the source region and along a lower portion of the trench sidewalls to provide a variable, lightly doped concentration that gradually decreases in density from the sidewalls of the trenches toward a plane about midway between the trenches.

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