Fin field-effect transistor device and method

A method of forming a semiconductor device, the method comprising:

• forming a first dummy gate and a second dummy gate over a fin;
• forming an interlayer dielectric layer (ILD) around the first dummy gate and the second dummy gate;
• and
• replacing the first dummy gate and the second dummy gate with a first metal gate and a second metal gate, respectively, wherein the replacing comprises:
• removing the first dummy gate and the second dummy gate to form a first recess and a second recess in the ILD, respectively;
• forming a gate dielectric layer in the first recess and in the second recess;
• forming a first work function layer in the second recess over the gate dielectric layer, wherein the gate dielectric layer in the first recess is exposed by the first work function layer;
• forming a second work function layer in the first recess and in the second recess using a same deposition process, wherein the second work function layer is formed to be thicker in the second recess than in the first recess;
• and
• filling the first recess and the second recess with a conductive material.

A method of forming a semiconductor device, the method comprising:

• forming a first dummy gate structure and a second dummy gate structure over a fin, the first dummy gate structure and the second dummy gate structure being surrounded by a dielectric layer;
• removing the first dummy gate structure and the second dummy gate structure to form a first recess and a second recess in the dielectric layer, respectively;
• forming a gate dielectric layer in the first recess and the second recess;
• forming a first work function layer in the second recess over the gate dielectric layer;
• converting a surface layer of the first work function layer into an oxide layer;
• forming a second work function layer in the first recess and the second recess, the second work function layer being over and contacting the gate dielectric layer in the first recess, the second work function layer being over and contacting the oxide layer in the second recess;
• and
• filling the first recess and the second recess with a gate material to form gate electrodes.