Very thin HfO2 films were deposited directly on Si substrates by the pulsed laser deposition technique in a wide range of substrate temperatures and oxygen pressures to investigate the kinetics of the interfacial layer formation. Angle-resolved X-ray photoelectron spectroscopy (XPS) investigations showed that the interfacial layer formed between the Si substrate and the deposited oxide contains a mixture of HfO2 and SiO2 without any strong evidence to support the formation of a silicate-type compound. X-Ray reflectivity measurements showed that the mass density of the interfacial layer is higher than that of pure SiO2, while spectroscopic ellipsometry measurements showed that the refractive index is higher than that of pure SiO2, therefore corroborating the XPS results. (C) 2003 Elsevier B.V. All rights reserved.