| 摘要 |
A phase change memory device having a word line contact includes an N+ base layer formed in a surface of a semiconductor substrate. A word line is formed over the N+ base layer. The word line contact is formed to connect the N+ base layer to the word line. The word line contact includes a first contact plug, a barrier layer formed on the first contact plug, and a second contact plug formed on the barrier layer coaxially with the first contact plug. The barrier layer prevents unwanted etching of the first contact plug when the second contact plug is being formed.
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