High quality TiO2 film grown by MOCVD on p-type GaAs with (NH4)(2)S treatment was obtained. The characteristics of TiO2/GaAs MOS capacitor were further improved by post-metallization annealing treatment. The leakage current densities can reach 1.7 x 10(-6) and 4.5 x 10(-5) A/cm(2) at +/- 2 V (2.7 MV/cm). The equivalent oxide thickness can reach 0.53 nm for the physical thickness of 7.5 nm. The dielectric constant is 52. The lowest interface state density is 4.7 x 10(11) cm(-2) eV(-1) derived by the high-low frequency capacitance method. (C) 2012 Elsevier Ltd. All rights reserved.