Replacement gate semiconductor device

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

• forming a dummy gate structure on a first device region;
• implanting at least one of a source and a drain region adjacent the dummy gate structure;
• removing the dummy gate structure after the implanting;
• forming a gate dielectric layer on the first device region after removing the dummy gate structure;
• forming an etch stop layer on the gate dielectric layer;
• and
• forming a metal gate electrode on the etch stop layer, wherein the metal gate electrode includes a work function layer formed on the etch stop layer.

A semiconductor device, comprising:

• a semiconductor substrate;
• a first gate structure formed on the semiconductor substrate, wherein the first gate structure includes a gate dielectric layer, an etch stop layer, a first work function metal, a second work function metal, and a fill metal;
• and
• a second gate structure formed on the semiconductor device, wherein the second gate structure includes the gate dielectric layer, the second work function metal, and the fill metal.