Polycrystalline TiO2 film with the thickness of 4 nm prepared by atomic layer deposition (ALD) on ammonium sulfide treated p-type InP shows a good interface quality but with slightly higher leakage current mainly resulted from the thermionic emission and grain boundary. Stacked with a high band-gap amorphous Al2O3 of 3 nm prepared by atomic layer deposition on TiO2, the leakage currents are improved to 1.9 x 10(-8) and 1.1 x 10(-8) A/cm(2) at +/- 2 MV/cm. The equivalent dielectric constant of Al2O3/TiO2 is about 18. The lowest interface state density is around 5.7 x 10(11) cm(-2) eV(-1). The fabricated enhancement-mode n-channel sulfur-treated InP MOSFET exhibits good electrical characteristics with a maximum transconductance of 135 mS/mm and electron channel mobility of 275 cm(2)/V s. (C) 2014 Elsevier Ltd. All rights reserved.