Provided are methods of forming a phase change memory device. A semiconductor device having a lower electrode and an interlayer insulating layer may be prepared. The lower electrode may be surrounded by the interlayer insulating layer. Source gases, a reaction gas and a purge gas may be injected into a process chamber of a semiconductor fabrication device to form a phase change material layer on a semiconductor substrate. The source gases may be simultaneously injected into the process chamber. The phase change material layer may be in contact with the lower electrode through the interlayer insulating layer. The phase change material layer may be etched to form a phase change memory cell in the interlayer insulating layer. An upper electrode may be formed on the phase change memory cell.