Amorphous and uniform silicon nitride films with thicknesses of less than 100 A˚ have been thermally grown on silicon wafers by employing purified ammonia gas. The films are much denser than conventional CVD Si3N4films. The MNS (metal‐thermal nitride‐silicon) structures have very lowNssin the order of 3×1010cm−2eV−1and an effective electron mobility of larger than 800 cm2/V sec in the fabricatedn‐channel MNSFFT.