Patent ID: 7670869

Claim:
A method for forming a memory device, comprising: providing a substrate; forming a first inter-layer dielectric layer on the substrate; forming a bottom electrode in the inter-layer dielectric layer; forming a first electrode layer on the first inter-layer dielectric layer and the bottom electrode; forming a dielectric layer on the first electrode layer; forming a second electrode layer on the dielectric layer; patterning the first electrode layer, the dielectric layer and the second electrode layer to form a pillar structure, corresponding to a memory cell of the memory device; forming a phase change layer on the pillar structure and the substrate; patterning the phase change layer to separate the patterned phase change layer of the memory cell from another patterned phase change layer of an adjacent memory cell, wherein the patterned phase change layer covers a surrounding of the pillar structure; and forming a top electrode, electrically connecting the second electrode layer of the pillar structure through the patterned phase change layer covering the surrounding of the pillar structure, wherein the pillar structure is column-shaped and wherein an interface between the first electrode layer and the phase change layer is ring-shaped.