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Trench MOSFET having drain-drift region comprising stack of implanted regions

  • US 20060038223A1
  • Filed: 08/23/2005
  • Published: 02/23/2006
  • Est. Priority Date: 07/03/2001
  • Status: Abandoned Application
First Claim
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1. A power MOSFET comprising:

  • a substrate of a first conductivity type;

    an epitaxial layer on said substrate, said epitaxial layer generally being of a second conductivity type opposite to said first conductivity type, a trench being formed in said epitaxial layer, a bottom of said trench being located in said epitaxial layer;

    an insulating layer lining said bottom and a sidewall of said trench;

    a conductive gate in said trench;

    a source region adjacent a surface of said epitaxial layer; and

    a drain-drift region of said first conductivity type extending through said epitaxial layer from said bottom of said trench to said substrate, said drain-drift region forming a PN junction with a portion of said epitaxial layer of said second conductivity type, wherein said drain-drift region comprises a vertical stack of overlapping implanted regions and wherein a doping concentration in a vertical cross-section of said drain-drift region starting at said bottom of said trench increases monotonically with increasing distance below said bottom of said trench over the entire distance to said substrate.

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