The thermal stabilities of the atomic layer deposited HfO2 films were investigated on HF-cleaned InP substrates with and without additional (NH4)(2)S cleaning. An abrupt interface without any interfacial layer between the HfO2 film and InP substrate was maintained during annealing at up to 600 degrees C for both samples. The S-passivation resulting from the (NH4)(2)S cleaning reduced the interface defect density, thereby decreasing the frequency dispersion and low-field leakage current. The increase of the capacitance equivalent SiO2 thickness after the thermal annealing was also delayed by the S-passivation, which was possibly attributed to the retardation of substrate materials diffusion into the HfO2 film. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.010112jes] All rights reserved.