Titanium oxide films were deposited by the ultrasonic spray pyrolysis process using titanium oxide acetylacetonate (TAAc) as source material dissolved in pure methanol. As-deposited films show the anatase crystalline structure, while annealed samples at 850degreesC have the rutile phase. Rutherford backscattering measurements indicate that the deposited films are formed by stoichiometric TiO2 material. Root-mean-square (rms) roughness depends on the substrate temperature and on the annealing process. Refractive index has values of the order of 2.36 for as-deposited films and 2.698 for annealed films. This change is associated with the anatase to rutile phase change. IR analyses show well-defined absorption peaks located at 433 and 638 cm(-1) for anatase phase and peaks located at 419, 466, 499 and 678 cm(-1) for rutile phase. In general, the titanium oxide films show high optical transmission. The energy band gap calculated for the anatase phase is of the order of 3.4 eV. The current density-electric field characteristics of MOS structures show current injection across the titanium oxide film even for low applied electric fields. However, electric breakdown was not observed for applied fields up to 5 MV cm(-1). (C) 2002 Elsevier Science B.V. All rights reserved.