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Method of making a high voltage DMOS transistor

  • US 4,626,293 A
  • Filed: 06/27/1984
  • Issued: 12/02/1986
  • Est. Priority Date: 06/27/1983
  • Status: Expired due to Term
First Claim
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1. A process for making a semiconductor device comprising the steps of:

  • providing a substrate of a first conductivity type;

    covering said substrate with an oxide layer;

    forming a polysilicon gate on said oxide layer;

    forming an opening in said oxide layer;

    subjecting said substrate to a first predeposition of impurity material of a second conductivity type through said opening;

    subjecting said substrate to a first diffusion drive-in operation to form a well of said second conductivity type therein through said opening;

    subjecting said substrate to a second predeposition and second diffusion drive-in steps of impurity material to form a region in said well through said opening separated from the boundary of said well by a channel zone, said channel zone being formed under said polysilicon gate;

    covering said polysilicon gate by a silicon nitride layer during at least said first drive-in step; and

    wherein said region forms the source of said device and said substrate forms the drain of said device.

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