Aluminum nitride films have been deposited on silicon substrates at 800°–1200°C by the pyrolysis of an aluminum trichloride‐ammonia complex, , in a gas flow system. The deposit was transparent, tightly adherent to the substrate, and was confirmed to be aluminum nitride by x‐ray and electron diffraction techniques. The deposited aluminum nitride films were found to be polycrystalline with the crystallite size increasing with increasing temperature of deposition. Other properties of aluminum nitride films relevant to device applications, including density, refractive index, dissolution rate, dielectric constant, and masking ability, have been determined. These properties indicate that aluminum nitride films have potential as a dielectric in electronic devices.