A method of fabricating a semiconductor device includes preparing a layout of the semiconductor device, obtaining contrast of an exposure image of the layout through a simulation under a condition of using a crosspole illumination system, separating the layout into a plurality of sub-layouts based on the contrast of the exposure image, forming a photomask having a mask pattern corresponding to the plurality of sub-layouts, and performing an exposure process using the photomask under an exposure condition of using a dipole illumination system.