A method of forming a phase change layer using a Ge compound and a method of manufacturing a phase change memory device using the same are provided. The method of manufacturing a phase change memory device included supplying a first precursor on a lower layer on which the phase change layer is to be formed, wherein the first precursor is a bivalent precursor including germanium (Ge) and having a cyclic structure. The first precursor may be a cyclic germylenes Ge-based compound or a macrocyclic germylenes Ge-based, having a Ge—N bond. The phase change layer may be formed using a MOCVD method, cyclic-CVD method or an ALD method. The composition of the phase change layer may be controlled by a deposition pressure in a range of 0.001 torr-10 torr, a deposition temperature in a range of 150° C. to 350° C. and/or a flow rate of a reaction gas in the range of 0-1 slm.