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MOS transistor with high breakdown voltage

  • US 5,191,401 A
  • Filed: 11/07/1991
  • Issued: 03/02/1993
  • Est. Priority Date: 03/10/1989
  • Status: Expired due to Term
First Claim
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1. A semiconductor device comprising:

  • a semiconductor substrate of a first conductivity type;

    a plurality of wells of a second conductivity type formed in said semiconductor substrate;

    a plurality of FET structure each having a drain electrode, with each of said structures formed in a different one of said wells; and

    a wiring layer extracted from said drain electrode outside said semiconductor substrate;

    wherein at least one of said FET structure includes;

    a first impurity diffusion layer of the first conductivity type formed in said one of said wells without contacting said semiconductor substrate;

    a second impurity diffusion layer of the second conductivity type which surrounds said first impurity diffusion layer and has an impurity concentration higher than that of said well;

    a third impurity diffusion layer of the first conductivity type formed within said second impurity diffusion layer without contacting said semiconductor substrate and said first impurity diffusion layer, said third impurity diffusion layer being ring-shaped and having a gap therein through which said wiring layer extends;

    a source electrode connected to both said second impurity diffusion layer and said third impurity diffusion layer;

    a gate electrode formed between said first impurity diffusion layer and said third impurity diffusion layer and formed on said second impurity diffusion layer so as to interpose an insulation film therebetween; and

    a drain electrode connected to said first impurity diffusion layer.

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