Disclosed are semiconductor devices and methods of manufacturing the same. The method comprises forming an active structure including a plurality of active patterns, a device isolation layer defining the active patterns, and a gate structure across the active patterns and extending in a first direction, forming a first mask pattern on the active structure, and forming a trench by using the first mask pattern as an etching mask to pattern the active structure. Forming the first mask pattern comprises forming in a first mask layer a plurality of first openings extending in a second direction intersecting the first direction, and forming in the first mask layer a plurality of second openings extending in a third direction intersecting the first and second directions.