A method of forming a pattern includes: preparing a target substrate including a photoresist layer on a base substrate; aligning a phase shift mask to the target substrate, the phase shift mask including a mask substrate comparted into a first region including a first sub region and second sub regions at sides of the first sub region, and second regions at sides of the first region, the phase shift mask including a phase shift layer on the mask substrate corresponding to the first region; fully exposing the photoresist layer at the first sub region and the second regions by utilizing the phase shift mask; and removing the photoresist layer at the first sub region and the second regions to form first and second photoresist patterns corresponding to the second sub regions. Transmittance of the phase shift layer is selected to fully expose the photoresist layer in the first sub region.