Replacement gates to enhance transistor strain

An apparatus comprising:

• an NMOS transistor having a strained first channel on a substrate, wherein the NMOS transistor includes a p-well on the substrate, the strained first channel between n-doped regions in the p-well, and a first gate structure on the strained first channel, the first gate structure including a high-k gate dielectric, an n-type work function metal, and a gate electrode fill material that provides a tensile strain in the strained first channel, wherein the gate electrode fill material that provides the tensile strain comprises at least one of titanium, and titanium carbide;
• and
• a PMOS transistor having a strained second channel on the substrate, wherein the PMOS transistor includes an n-well on the substrate, and a second gate structure over the strained second channel.