Patent ID: 8492259

Claim:
A method of forming metal gate structure, comprising: providing a substrate; forming a gate dielectric layer, a material layer and a poly-silicon layer stacked on the substrate; forming a first mask layer on the poly-silicon layer; forming a second mask layer on the first mask layer; forming a patterned photoresist on the second mask layer; removing portions of the second mask layer and portions of the first mask layer to form a hard mask including a first hard mask and a second hard mask by utilizing the patterned photoresist as an etching mask; removing the patterned photoresist; removing portions of the poly-silicon layer and portions of the material layer to form a gate stack by utilizing the hard mask as an etching mask after removing the patterned photoresist while the first hard mask of the hard mask being remained; forming two source/drain regions in the substrate at the two opposite sides of the gate stack respectively; and performing an etching process to remove the first hard mask of the hard mask after the two source/drain regions is formed.