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Fabrication of trench DMOS device having thick bottom shielding oxide

  • US 8,252,647 B2
  • Filed: 08/31/2009
  • Issued: 08/28/2012
  • Est. Priority Date: 08/31/2009
  • Status: Expired due to Fees
First Claim
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1. A method for fabricating a semiconductor device comprising:

  • a) forming a trench in the semiconductor layer;

    b) forming an oxide-nitride-oxide (ONO) structure on a sidewall and at a bottom of the trench, wherein the ONO structure includes a nitride layer between first and second oxide layers, wherein forming the ONO structure includes forming a first oxide layer on the sidewall and at the bottom of the trench and on top of the semiconductor layer;

    forming a nitride layer on top of the first oxide layer; and

    forming a second oxide layer on top of the nitride layer; and

    c) forming one or more conductive structures in a portion of the trench not occupied by the ONO structure, wherein the one or more conductive structures include a shield gate structure having an insulating material sandwiched between a first conductive structure and a second conductive structure, wherein forming the second oxide layer includes;

    filling the trench with the second oxide layer;

    etching back the second oxide layer to leave a portion of the second oxide at the bottom of the trench;

    forming a spacer layer with the predetermined thickness T1 on the second oxide layer and on the sidewalls of the remaining portions of the trench;

    anisotropically etching the spacer layer to form one or more spacers on the sidewall;

    anisotropically etching the second oxide layer to a non-zero thickness T2 at the bottom of the trench; and

    removing the one or more spacers.

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