Disclosed are semiconductor devices and methods of manufacturing the same. The method comprises sequentially forming a target layer and a first mask layer on a substrate, patterning the first mask layer to form a first opening in the first mask layer, forming a spacer covering an inner wall of the first opening, forming on the first mask layer a first photoresist pattern having a second opening vertically overlapping at least a portion of the spacer, forming a third opening in the first mask layer that is adjacent to the first opening by using the spacer as a mask to remove a portion of the first mask layer that is exposed to the second opening, and using the first mask layer and the spacer as a mask to pattern the target layer.