The high‐temperature behavior of TiSi2films, deposited on a polygate structure, was studied by means of Auger electron spectroscopy and low‐energy ion scattering. Both techniques reveal that upon heating at temperatures in excess of 600 °C the surface of the silicide film becomes Si‐enriched to an extent corresponding to TiSi4. This observation is in qualitative agreement with the theory of surface segregation, which predicts enrichment of the element with the lowest heat of vaporization. However, the effect is found not to be restricted to the topmost atomic layer, but extends to a depth of 30–40 Å. With oxygen, introduced into the vacuum system to a level of 10−6–10−4Torr, the same amount of enrichment is obtained, now at 500–600 °C. In this temperature range Ti desorbs from the silicide as TiOx.Apart from the outer surface layer the silicide is not oxidized under these circumstances. At higher temperatures, around 800 °C, this reactive adsorption–desorption of oxygen does not result in the formation of a thicker oxide layer but leads to a decomposition of the silicide. The attendant loss of Si and Ti, as measured with Rutherford backscattering, causes a severe roughening of the film surface.