Single layer TiO2 films deposited on BK7 glass substrates by the ion-assisted electron-beam evaporation technique have been characterized by phase modulated spectroscopic ellipsometry. The ellipsometry spectra were recorded in the wavelength range of 300-1000 nm. The measured spectra were then fitted with theoretically simulated curves generated assuming different model sample structures. Analyses were carried out separately in three different wavelength regimes, the transparent regime with no dispersion of refractive index (650- 1000 nm), the transparent regime with dispersion of refractive index (400-650 nm) and the absorbing regime (300-450 nm). Modeling has been attempted with both homogeneous and inhomogeneous sample structures. For the inhomogeneous structure, both linear and non-linear variation of refractive index along the depth of the sample were used. Refractive indices of the samples were determined separately from the best-fit ellipsometric data in the above three wavelength regimes. Finally, variation of refractive index with the variation in ion beam currents has been studied.