The accumulation capacitance of metal insulator-Si capacitors with SrTa2O6, ZrSiO4-based high-k gate dielectrics is observed to have significantly different dependence on the temperature and the frequency of a capacitance-voltage measurement than that of the conventional metal-oxide-Si capacitors. It is shown that this is due to contributions from the, often, inadvertently grown, and relatively poorer quality interfacial dielectric between the high-k material stack and the Si substrate. (C) 2002 Elsevier Science Ltd. All rights reserved.