In a photolithography process, a photoresist layer is formed on a substrate. A photomask is aligned over the substrate to transfer pattern images defined in the photomask on the substrate. The photomask includes first and second patterns of different light transmission rates, and a dummy pattern surrounding the second pattern having a light transmission rate lower than that of the first pattern. The substrate is exposed to a light radiation through the photomask. The photoresist layer then is developed to form the pattern images. The dummy pattern is dimensionally configured to allow light transmission, but in a substantially amount so that the dummy pattern is not imaged during exposure.