In this paper, we have correlated electrical measurements of thin HfO2 layers deposited on SiO2 by atomic layer deposition with angle-resolved X-ray photoelectron spectroscopy experiments. Results show that the HFO2/Si interface layer (IL) is made of a SiOx layer underneath a Si-rich Hf-sificate layer. The increasing of the IL thickness, during annealing, was essentially due to the silicon oxidation by -OH groups remaining in the HfO2 layer after deposition. Using shorter water pulse time, we were able to limit the SiOx growth during deposition. We have also observed, after annealing at 800 degreesC under nitrogen, a decreasing of the interfacial layer electrical thickness as well as an improvement of the equivalent oxide thickness of the stack. (C) 2003 Elsevier Ltd. All rights reserved.