Patent ID: 8476126

Claim:
A method for making a semiconductor device, comprising: providing a substrate; forming a high-k dielectric layer over the substrate; forming a first capping layer over the high-k dielectric layer, wherein the first capping layer includes titanium nitride; forming a second capping layer over the first capping layer, the second capping layer being different than the first capping layer, wherein the second capping layer includes tantalum nitride; after forming the first and second capping layers, forming a dummy gate layer over the first and second capping layers; performing a patterning process to form a gate stack including the high-k dielectric layer, first and second capping layers, and dummy gate layer; removing the dummy gate layer from the gate stack, thereby forming an opening that exposes the second capping layer; and filling the opening with a first metal layer over the exposed second capping layer and a second metal layer over the first metal layer, wherein the first metal layer is different from the second metal layer and has a work function suitable to the semiconductor device.