Epitaxial buffer layers enable the many functionalities found in perovskites to be integrated with silicon. However, epitaxial growth of SrTiO3 on silicon is tricky and has so far only been achieved by molecular beam epitaxy. Nonetheless, previous investigations of these films were limited by the amorphous layer occurring at the interface. Through a combination of improved interface quality and an improved model, we report the optical properties of SrTiO3 films on Si(100) investigated by spectroscopic ellipsometry. We find that the data are best described by a model with two different SrTiO3 layers, potentially resulting from variations in the oxygen content.