A method of fabricating a semiconductor device includes forming a plurality of pillar patterns on a substrate, filling a gap between the pillar patterns with a first conductive layer, forming a first hard mask layer pattern over the pillar patterns adjacent in one direction, etching the first conductive layer using the first hard mask layer pattern as an etch barrier, forming a second hard mask pattern over the pillar pattern adjacent in the other direction that crosses the one direction, and forming a gate electrode surrounding the pillar patterns by etching the first conductive layer etched using the second hard mask layer pattern as an etch barrier.