Semiconductor device and method of manufacturing the same

摘要

A MOS transistor includes a substrate, source/drain regions formed at portions of the substrate, and a channel region formed between the source/drain regions. The MOS transistor further includes a gate structure having a gate insulation layer pattern and a gate electrode formed on the channel region. The gate electrode includes a first gate conductive layer pattern and a second gate conductive layer pattern. The first gate conductive layer pattern has a nitrogen concentration gradient gradually increasing from a lower portion of the first gate conductive layer pattern to an upper portion of the first gate conductive layer pattern. The second gate conductive layer pattern includes a material having a resistance substantially lower than a resistance of the first gate conductive layer pattern.