Method for fabricating semiconductor device

A method for fabricating a semiconductor device, comprising:

• forming an N-type polysilicon layer and a P-type polysilicon layer over a substrate including an N-channel metal-oxide semiconductor (NMOS) region and a P-channel metal-oxide semiconductor (PMOS) region, the N-type polysilicon layer formed in the NMOS region and the P-type polysilicon layer formed in the PMOS region;
• forming a metal electrode layer over the N-type and P-type polysilicon layers;
• forming a gate hard mask over the metal electrode;
• forming a patterned buffer layer for defining gate pattern regions over the gate hard mask;
• forming a photoresist pattern exposing the PMOS region;
• trimming the patterned buffer layer in the PMOS region;
• removing the photoresist pattern;
• and
• etching the metal electrode layer and the N-type and P-type polysilicon layers to form gate patterns using the patterned and trimmed buffer layer.