Results of ellipsometric measurements performed in the W-vis and NIR spectral range on polysilicon films deposited on SiO2 spacer layers or directly onto silicon are presented. The effective medium approximation (EMA) based on the reference dielectric functions of a-Si and c-Si do not properly fit the ellipsometric spectra of thick polysilicon layers often characterized by large grains and rough surfaces. A multi layer model based on the experimental determined dielectric function of polysilicon measured at thinner layers is presented which fits the ellipsometric spectra well. Spectroscopic ellipsometry in the NIR is especially suitable for the measurement of thicker layers directly deposited on silicon.