Patent ID: 8343865

Claim:
A method of forming a semiconductor device, comprising: forming an interface layer on a semiconductor substrate having a first region and a second region; forming a first dummy metal gate layer on the interface layer, forming a first work function metal on the first dummy metal gate; forming a second dummy metal gate layer on the first work function metal; selectively removing the first dummy metal gate layer, the first work function metal and the second dummy metal gate layer on the first region of the semiconductor substrate, to leave the interface layer on the first region; forming a second work function metal different from the first work function metal on the interface layer on the first region and the second dummy metal gate layer on the second region; forming a third dummy metal gate layer on the second work function metal on the first and second regions; annealing to diffuse the second work function metal into the interface layer on the first region and the first work function metal into the interface layer on the second region; removing the second work function metal and the third dummy metal gate layer on the first region, and the first to third dummy metal gate layers and first and second work function metals on the second region, to leave the interface layer; and forming a high-k insulator on the interface layer on the first and second regions.