A method for fabricating a semiconductor device includes forming a gate insulation layer over a substrate, forming a first gate conductive layer over the gate insulation layer, forming a barrier metal over the first gate conductive layer, sequentially forming a second gate conductive layer and a gate hard mask over the barrier metal, patterning the gate hard mask, the second gate conductive layer, the barrier metal, the first gate conductive layer, and the gate insulation layer to form a gate pattern, and performing a plasma selective gate re-oxidation process on the gate pattern.