US Patent 7230287 Chevron CMOS trigate structure

Disclosed herein is a structure with two different type tri-gate MOSFETs formed on the same substrate. Each MOSFET comprises a fin with optimal mobility for the particular type of MOSFET. Due to the processes used to form fins with different crystalline orientations on the same substrate, one of the MOSFETs has a fin with a lower mobility top surface. To inhibit inversion of the top surface, this MOSFET has a gate dielectric layer with a thicker region on the top surface than it does on the opposing sidewall surfaces. Additionally, several techniques for forming the thicker region of the gate dielectric layer are also disclosed.