A method of forming a phase change layer may include providing a bivalent first precursor having germanium (Ge), a second precursor having antimony (Sb), and a third precursor having tellurium (Te) onto a surface on which the phase change layer is to be formed. The phase change layer may be formed by CVD (e.g., MOCVD, cyclic-CVD) or ALD. The composition of the phase change layer may be varied by modifying the deposition pressure, deposition temperature, and/or supply rate of reaction gas. The deposition pressure may range from about 0.001-10 torr, the deposition temperature may range from about 150-350° C., and the supply rate of the reaction gas may range from about 0-1 slm. Additionally, the above phase change layer may be provided in a via hole and bounded by top and bottom electrodes to form a storage node.