A phase-change memory device includes a word line on a substrate and a phase-change memory cell on the word line and comprising a phase-change material pattern. The device also includes a non-uniform conductivity layer pattern comprising a conductive region on the phase-change material pattern and a non-conductive region contiguous therewith. The device further includes a bit line on the conductive region of the non-uniform conductivity layer pattern. In some embodiments, the phase-change memory cell may further include a diode on the word line, a heating electrode on the diode and wherein the phase-change material layer is disposed on the heating electrode. An ohmic contact layer and a contact plug may be disposed between the diode and the heating electrode.