Patent ID: 8921178

Claim:
A method of making a semiconductor device, comprising: forming a dielectric layer over dummy gate electrodes overlying a semiconductor substrate having an N-channel region and a P-channel region; exposing an upper surface of said dummy gate electrodes; removing said dummy gate electrodes thereby forming trenches; forming a gate dielectric layer, a barrier conductive layer and a silicon layer in said trenches, wherein a thickness of said barrier conductive layer in trenches overlying said N-channel region is different from a thickness of said barrier conductive layer in trenches overlying said P-channel region; depositing a first metal on said silicon layer, said first metal being capable of undergoing a substitution reaction with silicon; and annealing said first metal so as to effect a substitution of said first metal for said silicon layer and removing a silicon-containing layer that is formed overlying said first metal by said substitution, said substitution of said first metal for said silicon layer forming a metal substituted layer.