The interaction of titanium films with single crystal silicon during rapid thermal annealing (RTA) has been studied by Auger analysis and SEM. The diffusion of silicon in titanium to form a silicide has been investigated as a function of the thickness of the interfacial silicon dioxide between the film and the substrate. For a clean interface the diffusion is initiated at lower temperatures, approximately 600 °C. Ion beam mixing of the interface caused by the implantation of heavy ions, such a arsenic, through the titanium film helps to render the interfacial oxide ineffective and thereby facilitates Si diffusion into the film. The presence of the interfacial oxide has been shown to affect the smoothness of the final silicide layer and the silicide–silicon interface. Silicide films produced from ion‐mixed films have been found to have smoother surfaces and interfaces than nonion‐mixed samples. Application of ion‐mixed films to devices has been studied.