Thin Eu-In oxide films were prepared on glass and Si (P) substrates to form metal-oxide-semiconductor (MOS) devices. These films were annealed at different conditions and characterised by UV-absorption spectroscopy, X-ray fluorescence (XRF), and X-ray diffraction (XRD). The ac-conductance and capacitance of the devices were studied as a function of frequency in the range of (500 Hz-100 kHz), temperature in the range of (293-363 K), and gate voltage. It was observed that the frequency dependence of the ac-conductivity and capacitance of the insulator is controlled by the "corrected barrier hopping" model, which based on the relaxation processes of hopping of current carriers between equilibrium sites. The temperature dependence of ac-conductance showing small activation energy characterises the hopping process. The method of capacitance-gate voltage (C-V-g) and conductance-gate voltage (G-V-g) were used to investigate the effect of annealing in air or in vacuum on the trapped-charge density in the oxide and the surface density of states (N-SS) at the insulator/semiconductor interface. It was observed that the prepared solid solution (SS) of Eu2O3-In2O3 has a sufficiently high dielectric constant (epsilon), around 30, which suggests that it is a promising candidate for high-epsilon dielectric applications. (c) 2004 Elsevier B.V. All rights reserved.