Patent ID: 8216948

Claim:
A method for forming a semiconductor device, comprising: providing a target substrate including a high density region and a low density region; forming an underlying layer and a first hard mask layer over the target substrate; patterning the first hard mask layer in the high density region and the low density region using a first exposure mask to form first hard mask patterns, the first exposure mask comprising a first exposure pattern formed in the high density region and a second exposure pattern formed in the low density region, wherein the first hard mask pattern in the high density region and the first hard mask pattern in the low density region have different widths; forming a first spacer over a sidewall of the first hard mask pattern in the high density region and a second spacer filling a space between neighboring first hard mask patterns in the low density region; etching the first spacer using a second exposure mask to form a first spacer pattern; removing the first hard mask patterns; forming a second hard mask layer in an opening defined by the first spacer pattern and the second spacer; removing the first spacer pattern and the second spacer such that the second hard mask layer remains; and etching the underlying layer using the second hard mask layer as an etch mask to form first and second target contact holes in the high density region and the low density region respectively.