Provided are a semiconductor memory device and a method of fabricating the same. The semiconductor memory device includes a heating portion interposed between a transistor and a data storing portion, and a metal interconnection layer connected to the data storing portion. The data storing portion includes a chalcogenide material layer which undergoes a phase change due to heating of the heating portion to store data therein. The heating material layer is disposed under the chalcogenide material layer, and the top surface of the heating material layer is oxidized using a plasma oxidation process to increase a resistance value. Accordingly, the heat capacity necessary for the chalcogenide material layer can be transmitted using a small amount of current, and current used in the semiconductor memory device can be further reduced.