Patent ID: 8008210

Claim:
A method for fabricating a semiconductor device, the method comprising: forming a first hard mask layer over a semiconductor substrate; forming a second hard mask layer over the first hard mask layer; etching the second hard mask layer using a photolithography process with an exposure mask to form a second hard mask pattern, wherein the exposure mask includes a rectangle shaped first light-blocking pattern rectangle shaped second light-blocking pattern to define a bit line contact region and the second light-blocking pattern is located diagonally from the first light-blocking pattern, wherein the second hard mask pattern includes a first pattern having a minor axis and in the direction of the minor axis, the first pattern of the second hard mask pattern is thicker along the minor axis at a centerline of the major axis than at a cross section of another part of the first pattern in the direction of the minor axis; forming a photoresist pattern using an exposing process with the exposure mask, the photoresist pattern overlying the second hard mask pattern; etching the first hard mask layer using the second hard mask pattern and the photoresist pattern as a mask to form a first hard mask pattern defining an active region; removing the second hard mask pattern and the photoresist pattern; and etching the semiconductor substrate using the first hard mask pattern to form a trench for device isolation.