The mobility in n-channel SOI MOSFETs exhibits a significant increase as the SOI film becomes thinner than 1000 Å. At a 500 Å SOI thickness, the mobility values are distributed in the 700–1100 cm2/Vs range, which are obviously higher than the value in a bulk MOSFET having an identical doping concentration. The observed mobility enhancement has been explained by a decrease in the vertical electric field, associated with the complete depletion of the SOI film.