The ultrathin SiO2 interfacial layer (IL) was adopted at the interface between atomic-layer-deposited HfO2 gate dielectric film and a Si substrate, which was grown using nitric acid oxidation (NAO) and O-3 oxidation (OZO) prior to Hf-2 film deposition. X-ray photoelectron spectroscopy result revealed that Si diffusion from the substrate into the film was suppressed for the film with NAO compared to that with OZO, which was attributed to the higher physical density of IL. The electrical measurement using metal-insulator-semiconductor devices showed that the film with NAO exhibited higher effective permittivity and lower densities of fixed charge and slow state at the interface. Furthermore, the leakage current density at an equivalent electrical thickness was lower for the film with NAO than OZO. (C) 2016 Elsevier B.V. All rights reserved.