Semiconductor device and method of forming the same

A semiconductor device, comprising:

• a semiconductor fin protruding above a substrate;
• a source epitaxy structure and a drain epitaxy structure on the semiconductor fin;
• and
• a gate structure between the source epitaxy structure and the drain epitaxy structure, the gate structure comprising a titanium nitride layer wrapping around the semiconductor fin, and a chlorine-containing N-work function metal layer wrapping around the titanium nitride layer.

A method, comprising:

• forming a fin extending from a substrate;
• forming a shallow trench isolation (STI) structure laterally surrounding a lower portion of the fin;
• forming a dummy gate structure wrapping around a channel region of the fin;
• forming a source epitaxy structure and a drain epitaxy structure respectively on opposite sides of the channel region of the fin;
• and
• replacing the dummy gate structure with a replacement gate structure, the replacing comprising depositing a chlorine-containing N-work function metal layer wrapping around the channel region of the fin, and depositing a tungsten layer wrapping around the chlorine-containing N-work function metal layer.