Amorphous aluminum oxide films were deposited at 420 °C by thermal decomposition of an aluminum alkoxide. The reducing or oxidizing atmosphere used during deposition affects the chemical and electrical properties of the oxide films. These films have shown superior characteristics when compared to SiO2 films deposited by a similar process under the same conditions. The dielectric properties of these Al2O3 films compare favorably with anodized Al2O3 films. The resistance of these films to moisture makes them attractive as coatings for passivation of electron devices. The electrical properties of silicon and germanium surfaces covered with these Al2O3 films vary according to the deposition atmosphere. © 1967, The Electrochemical Society, Inc. All rights reserved.