We report on the characteristics of metal-insulator-semiconductor (MIS) capacitors with aluminum nitride (AIN) as the dielectric material. Using reactive magnetron sputtering, we deposited layers of AIN on 1-10 Omega cm p-type (1 0 0) silicon wafers. The deposition rates were investigated as a function of sputter pressure, power, gas composition, and substrate tempterature. On films deposited over a range of sputter parameters, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) were performed indicating that optimal deposition conditions for best crystal quality and stoichiometry were a total pressure between 4 and 10 mT, a gas mixture of 85% nitrogen and 15% argon, and a substrate temperature approximate to 200 degreesC. The films had a weak microcrystalline structure with the c-axis preferentially orientated parallel to the substrate normal. MIS capacitors were fabricated on silicon substrates with Ti/Au contacts. Current-voltage (IV) and capacitance-voltage (CV) measurements revealed breakdown fields of 4-12 MV/cm. Depending on the thickness, leakage current densities were between 10(-10) and 10(-3) A/cm(2) at 1 V reverse bias. the interface charge density was less than or equal to 10(13) cm. and flat band voltages were from -10 to 2 V. The dielectric permittivity was between 4 and 11 for thick layers (greater than or equal to 100 Angstrom) and decreased to values between 2 and 6 for thicknesses below 100 Angstrom.