Phase change memory devices may include a semiconductor substrate of a first conductivity type and a plurality of parallel word lines disposed on the semiconductor substrate. The word lines may have a second conductivity type different from the first conductivity type and substantially flat top surfaces. First and second semiconductor patterns may be sequentially stacked on each word line, and an insulating layer may be provided to fill gap regions between the word lines, gap regions between the first semiconductor patterns and gap regions between the second semiconductor patterns. A plurality of phase change material patterns may be two-dimensionally arrayed on the insulating layer and electrically connected to the second semiconductor patterns.