Metal gate semiconductor device and method of fabricating thereof

A method, comprising:

• forming a portion of a first gate structure associated with a NMOS transistor, wherein the portion of the first gate structure includes a gate dielectric, a capping layer, a first metal layer on the capping layer, and a second metal layer overlying the first metal layer, wherein the first metal layer is an n-type metal;
• forming a portion of a second gate structure associated with a PMOS transistor, wherein the portion of the second gate structure includes the gate dielectric and the second metal layer formed on the gate dielectric, and wherein the second gate structure does not include the first metal layer;
• forming a dummy layer on the portion of the first gate structure and on the portion of the second gate structure overlying the second metal layer;
• removing the dummy layer simultaneously in both the first gate structure and the second gate structure to form trenches;
• and
• filling the trenches with a fill metal.

A method, comprising:

• forming a portion of a first gate structure associated with a first type of transistor, wherein the portion of the first gate structure includes a capping layer, a first metal layer having a first type of work function on the capping layer, and a second metal layer overlying the first metal layer;
• forming a portion of a second gate structure associated with a second type of transistor, wherein the portion of the second gate structure includes the gate dielectric and the second metal layer formed on the gate dielectric;
• treating the second metal layer of the first gate structure and the second gate structure;
• and
• forming a fill layer on the treated second metal layer of the first gate structure and the second gate structure.