Mos transistor and fabrication thereof

A method for fabricating a MOS transistor, comprising:

• forming a gate dielectric layer on a substrate;
• forming a first barrier layer on the gate dielectric layer;
• forming an interlayer on the first barrier layer;
• forming a work-function-dominating layer on the interlayer;
• forming a second barrier layer on the work-function-dominating layer;
• forming a poly-Si layer on the second barrier layer;
• patterning the poly-Si layer, the second barrier layer, the work-function-dominating layer, the interlayer and the first barrier layer into a gate;
• and
• forming a source/drain in the substrate beside the gate.