Increasing thickness of functional layer according to increasing recess area

A semiconductor device comprising:

• a semiconductor substrate comprising a plurality of semiconductor fins having first and second semiconductor fins;
• an insulating layer on the semiconductor substrate, the insulating layer comprising a lower portion surrounding lower portions of the semiconductor fins and a plurality of recesses having a first recess around an upper portion of the first semiconductor fin and a second recess around an upper portion
• of the second semiconductor fin;
• a gate dielectric layer on bottoms and sidewalls of the first and second recesses and on sidewalls and upper surfaces of the upper portions of the first and second semiconductor fins;
• a first work function adjustment layer on the gate dielectric layer;
• a functional layer on the first work function adjustment layer;
• and
• first and second gates on portions of the functional layer of the respective first and second semiconductor fins,
• wherein a surface area of a lateral opening of the first recess is larger than a surface area of a lateral opening of the second recess, and a thickness of a portion of the functional layer on the first semiconductor fin is greater than a thickness of a portion of the functional layer on the second semiconductor fin, wherein:
• the plurality of semiconductor fins further comprises a third semiconductor fin;
• the insulating layer further comprises a third recess around an upper portion of the third semiconductor fin;
• and
• a second work function adjustment layer on the first work function adjustment layer,
• wherein the first work function adjustment layer is a p-type work function adjustment layer, and the second work function adjustment layer is an n-type work function adjustment layer.