The electrical characteristics of metalorganic chemical vapor deposited TiO2 films on p-type GaAs were studied. For GaAs with (NH4)(2)S treatment, the electrical characteristics of TiO2/GaAs are improved from native oxide removal. The electrical characteristics can be further improved by hydrogen passivation on defects, grain boundary and interface of TiO2/GaAs via post-metallization annealing, in which the active hydrogen is produced from the reaction between aluminum (Al) contact and hydroxyl groups existed on oxide surface. The stack of liquid phase deposited high band-gap SiO2 on TiO2 film can lower the thermionic emission leakage of low band-gap TiO2 and improve the quality of stacked structure by fluorination. The leakage current densities of fluorinated-SiO2/PMA-treated TiO2/(NH4)(2)S-treated GaAs MOS structure can reach 5.4 x 10(-9) and 4.9 x 10(-7) A/cm(2) at +/- 1.5 MV/cm. The dielectric constant and the lowest interface state density are 39.7 and 4.8 x 10(11) cm(-2) eV(-1), respectively. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3603973] All rights reserved.