Yttrium oxide films deposited by-laser ablation on Si(100) substrates have been evaluated for possible application as high dielectric constant insulator layers. The structural, optical and electrical characteristics of these films have been determined by means of x-ray diffraction, atomic force microscopy, Auger electron spectroscopy, ellipsometry, infrared transmittance, and capacitance and current versus voltage (C-V and I-V) as a function of the deposition parameters. It has been found that the crystallinity of these films is strongly dependent on the substrate temperature during the deposition. At low deposition temperatures (350 degrees C) the films present an amorphous component and a polycrystalline part that is highly oriented in the (100) direction perpendicular to the surface of the film. As the deposition temperature is increased up to 650 degrees C, the amorphous part of the films is reduced drastically and the dominant orientation of the polycrystalline part becomes the (111) orientation. The refractive index at 630 nm was found to be in the range between 1.91 and 1.95, having its maximum value for films deposited at 450 degrees C. Similar behavior was observed for the dielectric constant kappa, measured from the high frequency capacitance measurements, with a maximum value of 15 obtained for the above mentioned` deposition temperature as well. The average roughness of the films decreases with substrate temperature from similar to 30 Angstrom to less than 5 Angstrom in the range of temperatures studied.