Titanium-doped erbium oxide films on Si(100) have been investigated as an alternative gate dielectric. The dielectric films were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and electrical measurements. We found that the addition of Ti into Er2O3 film after annealing at 700 degrees C can reduce the SiOx formation at the interfacial layer and thus reduce the O diffusion during the film postthermal annealing process. Such suppression effect significantly improved the electrical properties of the dielectric films.