Accurate characterization of the optical properties of thin film materials used in semiconductor manufacturing is essential for many metrology applications in the fab, including film thickness measurement and scatterometry. The most common method for measuring these optical properties is spectroscopic ellipsometry. In this work X-ray reflectometry is used as a means of independently determining the thickness of a film to be characterized. This information is then used in the conventional analysis of spectroscopic ellipsometry data to extract the optical properties. In addition, the use of a Cauchy dispersion model fitted to the transparent region of the spectrum (if it exists) was used to determine the film thickness. Once the thickness was determined, a point-by-point regression was performed on the ellipsometry data to extract the optical properties. The results from these techniques were compared with each other and with conventional analysis of the ellipsometry data using common dispersion models.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.