Patent ID: 7303981

Claim:
A method for forming a polysilicon structure, comprising: providing a substrate having a first region, a second region, and a third region; forming an amorphous silicon structure on the substrate with a first amorphous silicon region in the first region, a second amorphous silicon region in the second region, and a third amorphous silicon region in the third region, wherein the first amorphous silicon region is thinner than the second amorphous silicon region which is thinner than the third amorphous silicon region; and crystallizing the amorphous silicon structure to form the polysilicon structure with a first polysilicon region, a second region, and a third polysilicon region corresponding to the first amorphous silicon region, a second amorphous silicon region, and a third amorphous silicon region, respectively, wherein the first polysilicon region has a grain size larger than that of the second polysilicon region which has a grain size larger than that of the third polysilicon region.