The further development of MOSFET devices is mandatory for the development of information technology. Besides the optimization of lateral layouts and introduction of alternative device architectures, new materials were introduced, too. To increase the on current Ion the carrier mobility is increased by straining the silicon channel layer. To get strained silicon layers on insulator (SSOI) the so called Jülich-Process was developed, which uses an ion implantation assisted relaxation of thin Si1-xGex layer to get a high-quality surface to grow pseudomorphically strained silicon. To characterize the Si1-xGex, layers non-destructively by spectroscopic ellipsometry (SE), in this work a parametric expression of the dielectric function was established, which depends only on the Ge fraction x. With that function, SE can be used as powerful tool to characterize thickness and composition homogeneity of the epitaxial Si1-xGex, layers.