Annealing of high-permittivity HfTiO gate dielectric on Ge substrate in different gases (N(2), NH(3), NO and N(2)O) with or without water vapor is investigated. Analysis by transmission electron microscopy indicates that the four wet anneals can greatly suppress the growth of a GeO(x) interlayer at the dielectric/Ge interface, and thus decrease interface states, oxide charges and gate leakage current. Moreover, compared with the wet N(2) anneal, the wet NH(3), NO and N(2)O anneals decrease the equivalent permittivity of the gate dielectric due to the growth of a GeO(x)N(y) interlayer. Among the eight anneals, the wet N(2) anneal produces the best dielectric performance with an equivalent relative permittivity of 35, capacitance equivalent thickness of 0.81 nm, interface-state density of 6.4 x 10(11) eV(-1) cm(-2) and gate leakage current of 2.7 x 10(-4) A/cm(2) at V(g) = 1 V. (C) 2008 Elsevier B.V. All rights reserved.