In some embodiments, a method of manufacturing an integrated circuit device includes forming a feature structure on a substrate, forming a first hardmask configured to cover the feature structure, forming, on the first hardmask, a second hardmask comprising a plurality of first line portions extending lengthwise in a first horizontal direction and being apart from each other in a second horizontal direction perpendicular to the first horizontal direction, forming, on at least one of the first hardmask and the second hardmask, an etch mask pattern comprising a plurality of second line portions, forming, from the first hardmask, a first hardmask pattern comprising a plurality of third line portions, forming, from the second hardmask, a plurality of second hardmask patterns, and forming a feature pattern comprising a plurality of fourth line portions by etching the feature structure and using the plurality of second hardmask patterns and the first hardmask pattern.