A phase change memory (PCM) semiconductor device is provided. The PCM semiconductor device includes: a phase change material stack on a substrate, the phase change material stack including at least two phase change material layers each separated by an insulating layer; a first electrode on a first side of the phase change material stack; and a second electrode on a second side of the phase change material stack, wherein a first one of the phase change material layers has a length that is different from a length of a second one of the phase change material layers.