This paper describes the structural properties and electrical characteristics of thin erbium titanium oxide (Er2TiO5) as gate dielectrics deposited on silicon substrates through reactive radio frequency sputtering. The structural and morphological features of these films were explored by X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy measurements. It is found that the Er2TiO5 film prepared under a 4.5 nm Ti metal film and annealed at 700 degrees C exhibited a thinner capacitance equivalent thickness and excellent electrical properties than other films, including the leakage current density, interface trap density, and hysteresis in the capacitance-voltage curves. We attribute this behavior to the optimum titanium content in the metal oxide film which helps to suppress the information of the interfacial SiO2 and silicate at the Er2TiO5/Si interface. These materials also show negligible degrees of charge trapping at high electric field stress. (C) 2008 The Electrochemical Society.