Semiconductor device and method of fabricating the same

A semiconductor device comprising:

• a semiconductor substrate having a channel region;
• a gate dielectric layer over the channel region of the semiconductor substrate;
• a work function metal layer over the gate dielectric layer, wherein the work function metal layer comprises a first work function material;
• and
• a gate electrode over the work function metal layer, wherein at least a portion of the work function metal layer has a concentration of the first work function material reducing in a direction, and the direction is from the gate dielectric layer toward the gate electrode.

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

• forming a semiconductor fin;
• forming a gate dielectric layer over the semiconductor fin;
• depositing a first work function metal layer over the gate dielectric layer, the first work function metal layer having a first concentration of a work function material;
• depositing a second work function metal layer over the first work function metal layer, the second work function metal layer having a second concentration of the work function material, wherein the first concentration is higher than the second concentration;
• and
• forming a gate electrode over the second work function metal layer.