A memory device with improved heat transfer characteristics. The device first includes a dielectric material layer; first and second electrodes, vertically separated and having mutually opposed contact surfaces. A phase change memory element is encased within the dielectric material layer, including a phase-change layer positioned between and in electrical contact with the electrodes, wherein thelateral extent of the phase change layer is less than the lateral extent of the electrodes. An isolation material is positioned between the phase change layer and the dielectric layer, wherein the thermal conductivity of the isolation material is lower than the thermal conductivity of the dielectric material.