A method of manufacturing an integrated circuit device includes: over a substrate, forming first hard mask patterns extending in a first direction parallel to a top surface of the substrate and arranged at a first pitch in a second direction; forming a plurality of first trenches in the substrate using the first hard mask patterns as etching masks; forming a plurality of first gate electrodes on inner walls of the plurality of first trenches; over the substrate, forming second hard mask patterns extending in the first direction and arranged at a second pitch in the second direction; forming a plurality of second trenches in the substrate using the second hard mask patterns as etching masks, each of the plurality of second trenches being disposed between two adjacent first trenches; and forming a plurality of second gate electrodes on inner walls of the plurality of second trenches.