Patent ID: 8119478

Claim:
A phase-change random-access memory (PRAM) device, comprising: a first contact on a substrate, the first contact having a first cross-sectional area; a first phase change material on the first contact, the first phase change material having a first region in contact with the first contact; a second contact on the first phase change material, the second contact having a second cross-sectional area wider than the first cross-sectional area, the first phase change material having a second region being in contact with the second contact, wherein the second region is larger than the first region; wherein the first phase change material has a first programmable volume connected to the first region and a second programmable volume connected to the second region; and a second phase change material on the second contact, the second phase change material having a third region in contact with the second contact, the third region being the same size as the second region, wherein the second phase change material has a third programmable volume connected to the third region, and wherein the second cross-sectional area is narrower than a top surface of the first phase change material.