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Trench semiconductor device having gate oxide layer with multiple thicknesses and processes of fabricating the same

  • US 7,276,411 B2
  • Filed: 05/25/2005
  • Issued: 10/02/2007
  • Est. Priority Date: 05/25/1999
  • Status: Expired due to Fees
First Claim
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1. A process of fabricating a trench semiconductor device comprising:

  • providing a semiconductor material;

    forming a trench in said semiconductor material, said trench extending from a surface of said semiconductor material into said semiconductor material;

    after forming said trench, directionally depositing a first oxide layer on said semiconductor material, said first oxide layer depositing preferentially on horizontal surfaces so as to form a thick portion in a bottom of said trench and a thin portion on a sidewall of said trench, said thick portion being thicker than said thin portion;

    after depositing a first oxide layer, depositing a polysilicon layer, said polysilicon layer filling said trench and overflowing said surface of said semiconductor material;

    removing a sufficient amount of said polysilicon layer such that a surface of said polysilicon layer is substantially coplanar with said surface of said semiconductor material, said removing comprising chemical-mechanical polishing;

    forming a second oxide layer over said surfaces of said polysilicon layer and said semiconductor material;

    forming a mask layer over said second oxide layer; and

    etching said second oxide layer through an opening in said mask layer so as to leave a portion of said second oxide layer overlying said surface of said polysilicon layer and a portion of said surface of said semiconductor material.

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