Nonplanar device with thinned lower body portion and method of fabrication

A method of fabricating a nonplanar transistor, the method comprising:

• forming a semiconductor body above a substrate, the semiconductor body having a channel region comprising:
• a top surface;
• and
• a pair of laterally opposite sidewalls extending downward from the top surface;
• an upper body portion adjacent the top surface and above a middle body portion above a lower body portion, wherein a widest width of the upper body portion is located where the upper body portion meets the middle body portion, wherein the laterally opposite sidewalls of the middle body portion taper continually inward downward from the upper body portion to the lower body portion, and wherein the lower body portion has substantially vertical sidewalls;
• forming a gate dielectric layer on and in direct contact with the top surface and the sidewalls of the channel region on and in direct contact with the top surface and the sidewalls of the channel region including on and in direct contact with the laterally opposite sidewalls of the middle body portion which continually taper inward and including on and in direct contact with the substantially vertical sidewalls of the lower body portion;
• forming a gate electrode on the gate dielectric layer on the top surface and sidewalls of the channel region;
• and
• forming a pair of source/drain regions on opposite sides of the channel region.