Thermally stimulated currents (TSCs) have been measured to investigate electron traps in HfO2 prepared by reactive sputtering on silicon. Broken planes of the silicon crystal, which may contribute to the occurrence of interface states, were identified between the silicon and SiOx interlayer by transmission electron microscopy (TEM). A second domain was found between SiOx and HfO2 constituting a gradual transition region between the two oxides. This interface region was found to be a source of unstable charge traps where captured electrons interact with the silicon energy states through a combined tunneling and thermal process. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3530845] All rights reserved.