Different aspects of the reaction between Ti and single‐crystal (100) Si are reported when the reaction is thermally activated by rapid thermal annealing. The sheet resistance variation of the film was measured for a wide range of annealing temperatures, from 400° to 1100°C, in two different atmospheres of high purity Ar and gas, for bare and As‐implanted Si. At temperatures ≥800°C, the only silicide formed was . Both cross‐sectional TEM and RBS results indicate that the amount of titanium consumed in the reaction depends strongly on the atmosphere used for silicidation. Argon makes possible the reaction of almost the whole Ti layer with silicon, while nitrogen leaves an unreacted layer of about 15 nm, independent of the thickness of the original film. A two‐step anneal is necessary to eliminate bridging in a patterned oxide structure. No difference was observed in the roughness of the external surface whether the samples were annealed in Ar or in . No significant enhanced diffusion of As into Si was observed near the interface after RTA in an Ar ambient, while a redistribution of As into the silicide takes place. The As piles up at the surface, from which it evaporates at high temperatures. Results of furnace‐annealed samples in atmosphere show a pile‐up of As at the and the atmosphere interfaces, where it evaporates from the latter, at high temperatures.