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Method of making a trench mosfet with heavily doped delta layer to provide low on-resistance

  • US 5,688,725 A
  • Filed: 06/06/1995
  • Issued: 11/18/1997
  • Est. Priority Date: 12/30/1994
  • Status: Expired due to Term
First Claim
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1. A method of fabricating a vertical trench MOSFET, said method comprising the steps of:

  • providing a substrate of a first conductivity type;

    forming an epitaxial layer of said first conductivity type on a surface of said substrate;

    performing a first implant of dopant of said first conductivity type through a top surface of said epitaxial layer so as to form a delta implant region having a dopant concentration greater than a dopant concentration of a remaining portion of said epitaxial layer;

    performing a second implant of dopant of a second conductivity type that is opposite to said first conductivity type through said top surface of said epitaxial layer to form a deep diffusion;

    after said step of performing a first implant, forming a first trench and a second trench at said top surface, said first and second trenches defining a cell of said MOSFET, said deep diffusion being located in a central region between said first and second trenches, said deep diffusion not being in contact with either said first trench or said second trench;

    performing a third implant of dopant of said second conductivity type into said epitaxial layer to form a body implant region;

    performing a fourth implant of dopant of said first conductivity type into said epitaxial layer to form a source region; and

    depositing metal so as to form a contact with said source and body implant regions.

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