The alumina addition effect on Bi1-x-yTixAlyOz (BTAO) dielectric films was investigated with nanolaminate films of bismuth titanate and alumina layers. By the addition of alumina layers to the Bi-Ti system, the alumina content gradually increases but the Bi and Ti contents conversely decrease. The bandgap of BTAO increases to a certain level (4.1 eV) with the addition of alumina and then saturates. However, the difference between Fermi level and valence bandedge gradually increases as the alumina layers are added, making them more n-type material. The dielectric constant of BTAO decreases but the insulating property was improved by the addition of alumina layers. (c) 2006 The Electrochemical Society.