Tantalum and silicon oxides have been sputter deposited onto gallium arsenide using a 500-eV beam of neutralized argon atoms. MIS devices show very low leakage and capacitances that can be varied from full accumulation to depletion with the application of modest voltages. Other measurements (breakdown field, dielectric constant, adherence, Auger profile, and photoluminescence) also suggest that these structures hold potential usefulness for insulated-gate GaAs circuitry.