A method of correcting a designed pattern of a photomask for fabricating a semiconductor device is provided. A substrate is provided. A first mask pattern of the photomask designed to form a first contact pattern on the substrate is conceived. The first mask pattern includes a plurality of mask holes each having a hole size. The first mask pattern is adjusted to expand the hole size along a horizontal direction and rotate the mask holes for conceiving a second mask pattern of the photomask designed to form a second contact pattern having a plurality of contact holes. A plurality of device gaps between the contact holes is verified, and an overlay margin between the second contact pattern and an adjacent pattern in the semiconductor device is verified for determining whether the second contact pattern is the designed pattern of the photomask.