Patent ID: 8236686

Claim:
A method of forming dual metal gates, the method comprising: forming a first metal layer directly over a gate dielectric layer and a second metal layer directly over the first metal layer, wherein the second metal layer substantially covers the first metal layer; removing a portion of the second metal layer to expose the first metal layer in a first region; forming one silicon layer directly over the exposed first metal layer in the first region and directly over the second metal layer in a second region; annealing the first metal layer and the second metal layer within the second region, such that elements of the second metal layer are mixed with the first metal layer and a first work function of the first metal layer within the second region is altered to a second work function, wherein the first work function is different from the second work function; and etching to form the dual metal gates in the first and second regions after the forming of the one silicon layer, wherein the first region includes: a portion of the gate dielectric layer, a portion of the first metal layer directly over the gate dielectric layer, and a portion of the one silicon layer directly over the first metal layer, the portion of the first metal layer within the first region including the first work function, and wherein the second region includes: a portion of the gate dielectric layer, a portion of the first metal layer directly over the gate dielectric layer, a portion of the second layer directly over the first metal layer, and a portion of the one silicon layer directly over the second metal layer, the portion of the first metal layer within the second region including the second work function, and wherein a portion of the first metal layer in the second region is prevented from contacting the one silicon layer by the second metal layer.