Patent ID: 8551805

Claim:
A method comprising: forming a first mold layer on a substrate and having a first opening exposing a word line; forming a contact plug on the word line in the first opening; forming a second mold layer on the first mold layer and having a second opening exposing the contact plug; forming a heating electrode on the contact plug in the second opening; forming a third mold layer on the second mold layer and having a third opening exposing the heating electrode; forming a phase-change material pattern on the heating electrode in the third opening; forming a material layer on the phase-change material pattern and the third mold layer; forming a fourth mold layer on the material layer and having a fourth opening exposing a portion of the material layer on the phase-change material pattern; plasma hydrogenating to reduce the exposed portion of the material layer to a metal; plasma carbonizing the metal to form a metal carbide region; and forming a bit line on the metal carbide region.