Under the condition of excess metal deposition, the formation of Co and Ti silicides on (001) silicon-on-insulator (SOI) substrates was investigated. In the Co silicide case, a high-resistivity Co silicide film was formed after a high temperature anneal (1000 degrees C for 30 s). Transmission electron microscopy (TEM) revealed that the phase formed was CoSi. The phenomenon of CoSi being the most stable phase, instead of CoSi2, at high temperatures can be understood from both kinetics and thermodynamics. In the Ti silicide case, the most dominant phase was C49-TiSi2, therefore the film resistance was high even after high temperature annealing (900 degrees C for 20 s). The film morphology was thermally stable on further annealing and the resistance decreased gradually by means of partial transformation of C49-TiSi2 to the C54-TiSi2 phase. For device applications, high resistance silicide films are not desirable, therefore the metal thickness and consequent silicide thickness have to be controlled precisely.