Patent ID: 8168523

Claim:
A method for manufacturing a semiconductor device comprising: forming a first, a second and a third semiconductor layer over a substrate; forming a gate insulating layer over the first, the second and the third semiconductor layer; forming a conductive film over the gate insulating layer; forming a resist film over the conductive film; performing a light exposure to the resist mask by using an exposure mask to form a first mask layer, a second mask layer and a third mask layer; and etching the conductive film by using the first mask layer, the second mask layer and the third mask layer, wherein the exposure mask contains a first semi-transmissive film and a first light shielding portion stacked with each other, a second semi-transmissive film and a second light shielding portion stacked with each other, and a third semi-transmissive film and a third light shielding portion stacked with each other, and wherein the first semi-transmissive film has a same width as the first light shielding portion, the second semi-transmissive film is wider than the second light shielding portion, and the third semi-transmissive film is wider than the third light shielding portion.