The silicidation process of titanium on silicon shows three distinct ranges depending on the treatment temperature. From 700°C up to 900°C, a stable and reproducible TiSi2 C54/Si structure is formed for all treatment conditions. At lower temperatures the silicidation process is not complete, and several silicide phases appear during the thermal treatment. On the other hand, the silicidation at high temperatures (T>900°C) provokes changes in the TiSi2/Si structures. We have centred our interest in these two extreme ranges of temperature. The degree of silicidation has been established by Rutherford backscattering and grazing-incidence x-ray diffraction. It has been observed that TiSi and TiSi2 C54 are the only silicide phases present in the film at low temperatures. The distribution of phases has been determined by transmission electron microscopy. The high-resolution electron microscopy images indicate that the silicide/silicon interface is very flat, but the interface between the different phases of the silicide is not well defined. High-resolution electron microscopy and I–V measurements have been used to characterize the interface formed between the silicide and the silicon at high temperatures. At 1050°C the interface is flat in a scale of nanometres but it is rough in a scale micrometres. This roughening is not high enough to explain the decreasing of the Schottky barrier height. © 1997 John Wiley & Sons, Ltd.