A semiconductor memory device is disclosed, which relates to a technology for a serial cell structure of a phase change memory (PCM). The semiconductor memory device includes a plurality of unit cells stacked with a plurality of layers, and a single bit line formed to have a vertical structure and shared by the plurality of unit cells. Each unit cell includes a switching element including a source region, a drain region, and a channel region, and a phase change resistor (PCR) element formed over the switching element.