Method for fabricating semiconductor device

A method for fabricating semiconductor device includes the steps of: forming a gate structure on a substrate; forming a source/drain region adjacent to two sides of the gate structure; forming an interlayer dielectric (ILD) layer on the gate structure; forming a contact hole in the ILD layer to expose the source/drain region; forming a barrier layer in the contact hole; performing an anneal process; and performing a plasma treatment process to inject nitrogen into the contact hole.