A phase change memory device and a method of fabricating the same are provided. A phase change material layer of the phase change memory device is formed of germanium (Ge)-antimony (Sb)-Tellurium (Te)-based Ge2Sb2+xTe5 (0.12≦x≦0.32), so that the crystalline state is determined as a stable single phase, not a mixed phase of a metastable phase and a stable phase, in phase transition between crystalline and amorphous states of a phase change material, and the phase transition according to increasing temperature directly transitions to the single stable phase from the amorphous state. As a result, set operation stability and distribution characteristics of set state resistances of the phase change memory device can be significantly enhanced, and an amorphous resistance can be maintained for a long time at a high temperature, i.e., around crystallization temperature, and thus reset operation stability and rewrite operation stability of the phase change memory device can be significantly enhanced.