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Power semiconductor devices and methods

  • US 8,704,302 B2
  • Filed: 11/06/2012
  • Issued: 04/22/2014
  • Est. Priority Date: 05/28/2009
  • Status: Active Grant
First Claim
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1. A power semiconductor device, comprising:

  • a first-conductivity-type semiconductor substrate, and at least one second-conductivity-type epitaxial layer overlying and forming a junction with said substrate;

    at least one trench, extending downwardly into said epitaxial layer, which has dielectric material therein, and also includes vertically graded spatially fixed net electrostatic charge which tends to deplete adjacent second-conductivity-type semiconductor material;

    a semiconductor drift region, in said epitaxial layer, which extends down to said junction, and which has a dopant concentration which generally decreases with depth, EXCEPT that an additional concentration of said second-conductivity type dopants is present in said drift region at said junction;

    a semiconductor source region, which has said first conductivity type, and a semiconductor body region which has said second conductivity type and which separates said source region from said drift region; and

    at least one gate electrode which controls accumulation or depletion of a portion of said body region to thereby define a channel region therein;

    wherein, under at least some conditions, majority carriers pass from said source, through said channel and through said drift region to said substrate.

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