Ultrathin body (UTB) fully depleted silicon-on-insulator (FDSOI) devices show great performance due to undoped channels and excellent electrostatic control. Very high drive currents and good off-state leakage, ideal subthreshold slope, and small drain-induced barrier lowering (DIBL) have been reported with devices as short as 20 nm. The ultrathin channel enables high device performance, but it imposes a new set of problems. The control of the silicon thickness has become the dominant source of device variations. Selective epitaxial growth has become a necessity to achieve high performance and reliable contacts to UTB FDSOI devices. This work discusses silicon thickness control, selective epitaxial growth, and the mid-gap gate module needed for fully depleted devices. Very good control of short channel effect is shown and drive current fluctuations are discussed.