The integration of high-k dielectric materials into semiconductor devices requires nondestructive, fast, and accurate characterization methods. Spectroscopic ellipsometry (SE) is an outstanding candidate for this purpose. A multisample variable-angle SE method was used to characterize ZrO2 samples deposited on Si(100) by high-vacuum chemical vapor deposition. Proper modeling of the optical properties of the interfacial layer is found to be the key to accurate characterization of ZrO2 films. Based on a stacking model consisting of an effective medium approximation surface-roughness layer, a Tauc-Lorentz (TL) layer to represent the ZrO2 layer, and a second TL layer to represent the interfacial layer, we accurately extract both thickness and optical constants of each layer. The extracted surface-roughness and thickness values were confirmed by atomic force microscopy and transmission electron microscopy results. The optical constants of the interfacial layer suggest that the interfacial layer is composed of nonstoichiometric zirconium silicate. (C) 2004 American Vacuum Society.