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Dual depth trench isolation

  • US 6,875,697 B2
  • Filed: 08/24/2004
  • Issued: 04/05/2005
  • Est. Priority Date: 07/13/2001
  • Status: Expired due to Fees
First Claim
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1. A process for forming trench isolation in a semiconductor memory device, said process comprising the steps of:

  • forming a photoresist material over a silicon substrate;

    forming a photoresist pattern from said photoresist material to form a first, second and third level into said photoresist pattern, said first level defining active areas within said silicon substrate, said second level defining an intra-well width, an intra-well depth, a first inter-well width and a first inter-well depth, said third level defining a second inter-well width and a second inter-well depth;

    etching said silicon substrate by transferring said photoresist pattern thereto to form an inter-well trench having an overall combined width and depth comprising said first inter-well width, said first inter-well depth, said second inter-well width and said second inter-well depth, said step of etching simultaneously forming intra-well trenches on opposing sides of said inter-well trench;

    forming isolation material in said intra-well trenches and said inter-well trench;

    forming conductive wells having a common boundary but having opposite conductivity types within said define active areas, said isolation material interposed at said common boundary of said conductive wells.

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