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CMOS gate stack structures and processes

  • US 9,508,728 B2
  • Filed: 01/21/2016
  • Issued: 11/29/2016
  • Est. Priority Date: 06/06/2011
  • Status: Active Grant
First Claim
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1. A semiconductor device integrated circuit comprising:

  • a first device for SRAM comprising a first substantially undoped layer at a semiconductor surface, a first highly doped screening layer of a first conductivity type beneath the first substantially undoped layer, a first well of the first conductivity type beneath the first highly doped screening layer and a first gate stack on the first substantially undoped layer,a second device for SRAM comprising a second substantially undoped layer at the semiconductor surface, a second highly doped screening layer of a second conductivity type beneath the second substantially undoped layer, a second well of the second conductivity type beneath the second highly doped screening layer and a second gate stack on the second substantially undoped layer,a third device for logic comprising a third substantially undoped layer at the semiconductor surface, a third highly doped screening layer of a first conductivity type beneath the third substantially undoped layer, a third well of the first conductivity type beneath the third highly doped screening layer and a third gate stack on the third substantially undoped layer,a fourth device for logic comprising a fourth substantially undoped layer at the semiconductor surface, a fourth highly doped screening layer of a second conductivity type beneath the fourth substantially undoped layer, a fourth well of the second conductivity type beneath the fourth highly doped screening layer and a fourth gate stack on the fourth substantially undoped layer,shallow trench isolation regions separating the first device, the second device, the third deice and the fourth device,wherein each of the first gate stack, the second gate stack, the third gate stack and the fourth gate stack has a workfunction that is substantially midgap with respect to the semiconductor material.

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