US Patent 7675770 Phase change memory device

A phase change memory device, comprising a phase change memory device; a semiconductor substrate; a MOS transistor disposed at each intersection of a plurality of word lines and a plurality of bit lines arranged in a matrix form; a plurality of phase change memory elements for storing data of a plurality of bits, each formed on an upper area opposite to a diffusion layer of the MOS transistor in a phase change layer made of phase change material; a lower electrode structure for electrically connecting each of the plurality of phase change memory elements to the diffusion layer of the MOS transistor.