The thickness of thin cobalt and cobalt disilicide layers has been measured by spectroscopic ellipsometry (SE). The results obtained by this non-destructive technique are compared with measurements done by two well-established but destructive techniques, namely Rutherford backscattering spectrometry (RBS) and high resolution transmission electron microscopy (HREM). The thickness values obtained by SE are in good agreement with the values measured by RBS and HREM. Spectroscopic ellipsometry allows one to determine the thickness of the metal and silicide layers on device wafers, thereby avoiding the need to use destructive techniques on test wafers or fully processed device wafers.