Semiconductor device and method

A method comprising:

• forming a channel region over a semiconductor substrate;
• depositing a gate dielectric layer over the channel region;
• and
• forming a gate electrode over the gate dielectric layer, by:
• depositing a capping layer over the channel region,
• depositing a first work function metal layer over the capping layer, the first work function metal layer comprising aluminum (Al);
• exposing the first work function metal layer to a work function tuning gas to form a work function tuning layer on the first work function metal layer, wherein the concentration of aluminum in the first work function metal layer decreases from an interface between the first work function tuning layer and the capping layer to about halfway through the thickness of the first work function metal layer, and then increases to an interface between the first work function metal layer to the first work function tuning layer;
• and
• depositing a fill material over the first work function tuning layer.

A method comprising:

• forming an n-type channel region over a semiconductor substrate;
• forming a p-type channel region over the semiconductor substrate;
• depositing a first gate dielectric layer over the n-type channel region;
• depositing a second gate dielectric layer over the p-type channel region;
• depositing an n-type work function metal layer over the first gate dielectric layer;
• exposing the n-type work function metal layer to a work function tuning gas, the work function tuning gas comprising a transition metal chloride to form a first work function tuning layer is deposited over the n-type work function metal layer;
• forming a p-type work function metal layer over the second gate dielectric layer;
• and
• forming a p-type work function tuning layer by layer by forming a dopant containing layer on the p-type work function metal layer and driving dopants from the dopant containing layer into the p-type work function metal layer.