Patent ID: 7871915

Claim:
A method of fabricating a semiconductor device comprising: providing a semiconductor substrate having a first region and a second region; forming a high-k dielectric layer over the semiconductor substrate; forming a semiconductor layer over the high-k dielectric layer; forming a first gate stack in the first region and a second gate stack in the second region, the first and second gate stacks each including the high-k dielectric layer and the semiconductor layer; removing the semiconductor layer from the first gate stack to form a first trench and from the second gate stack to form a second trench; forming a barrier layer in the first trench and the second trench; forming a first metal layer over the barrier layer, such that the first metal layer includes TiN; removing at least a portion of the first metal layer in the first trench; forming a second metal layer in the first trench and in the second trench, such that the second metal layer includes a Ti layer and an Al layer on the Ti layer; and performing a thermal process at a temperature ranging from about 400 C to about 500 C to reflow the Al layer with the partially removed TiN layer in the first trench to form a TiAlN layer.