CMOS device and fabrication method

A method of forming a complementary metal-oxide-semiconductor (CMOS) device comprising:

• providing a semiconductor substrate including a first region and a second region;
• providing a first dummy gate structure including a first dummy gate over the semiconductor substrate in the first region and a second dummy gate structure including a second dummy gate over the semiconductor substrate in the second region;
• amorphizing a surface portion of the first dummy gate to form a first amorphous silicon layer on the first dummy gate;
• forming an interlayer dielectric layer on the semiconductor substrate, wherein the first amorphous silicon layer and the second dummy gate are exposed;
• wet etching the second dummy gate to form a second opening, while the first amorphous silicon layer protects the first dummy gate without forming a photoresist protective layer;
• forming a second metal gate in the second opening;
• removing the first amorphous silicon layer and the first dummy gate to form a first opening;
• and
• forming a first metal gate in the first opening.