Methods of manufacturing semiconductor devices

A method of manufacturing a semiconductor device includes forming an interlayer insulating layer on a substrate, forming a first mask layer on the interlayer insulating layer, forming a second mask layer and a first spacer on the first mask layer, forming a photoresist pattern on the second mask layer, forming a second mask pattern by patterning the second mask layer through a first etching process, forming a first mask pattern by patterning the first mask layer through a second etching process, forming a trench by etching a portion of the interlayer insulating layer through a third etching process, and forming an interconnection pattern within the trench. A width of the first mask pattern after the second etching process is less than a width of the photoresist pattern.