Field effect studies have been carried out on thin film InSb inert insulator solid-solid interfaces. The films were prepared by the protected recrystallization method, namely vacuum evaporation and subsequent annealing of the resulting insulator-semiconductor-insulator sandwiches. The high annealing temperatures permissible without danger of reevaporation of the more volatile component gave films with high mobility of approximately 103−104cm2/V-s and relatively low carrier concentrations of approximately 1016−1017/cm3. The good bonding of the insulator on to an inherently clean semiconductor surface resulted in a low fast surface state density of approximately 5 × 1011/cm2, which would permit the use of these films for field effect transistor applications. Thin films are very well suited for field effect investigations. Surface Hall effect and surface conductivity against surface potential gave the trapped and mobile charge density with the relevant Hall and field effect mobility directly. A model of fast surface states based on these results is proposed.