We fabricated Al/TiNx/(Ti/Si) x 15/Si(100) submicron devices by magnetron sputtering. Spectroscopic Ellipsometry (SE) was used for in situ characterization of TIN,, Ti and Si layers. The intermixing of Ti/Si layers and the phase transformations of TiSi during annealing were monitored by Kinetic Ellipsometry (KE). The metallic behavior of the TiNx layers was studied by analyzing their dielectric function in the IR region, measured by Fourier Transform InfraRed Spectroscopic Ellipsometry (FTIRSE), and by the unscreened plasma energy ((h) over bar omega(pu)) calculated by SE data analysis.