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Method for forming and tailoring the electrical characteristics of semiconductor devices

  • US 5,661,045 A
  • Filed: 12/09/1996
  • Issued: 08/26/1997
  • Est. Priority Date: 05/24/1993
  • Status: Expired due to Term
First Claim
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1. A method for fabricating semiconductor devices, comprising:

  • providing a substrate;

    forming active areas on the substrate;

    isolating the active areas with a field oxide;

    forming a mask on the substrate having openings therein for exposing selected active areas while protecting remaining active areas;

    implanting a dopant with sufficient energy such that the dopant penetrates through the field oxide and into the substrate for defining isolation field areas on the substrate and the dopant penetrates into the selected active areas;

    implanting a second dopant through the openings into the selected active areas, said second dopant comprising a different conductivity type than said dopant in order to lower a threshold voltage of a transistor to be formed in the selected active areas; and

    continuing processing to form active semiconductor devices in the active areas.

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