Auger electron spectroscopy (depth profiling and line shape analysis), X-ray diffraction, and cross-sectional transmission electron microscopy were employed to investigate the kinetics of titanium silicide formation by rapid thermal annealing in N2 and Ar ambients. A silicide is formed within only a few seconds at 620°–700°C. All the analysis techniques utilized reveal that the silicides primarily consist of sequential TiSi2 and TiSi phases. The TiSi2 is the metastable, poorly-conducting C49 modification. The TiSi2 growth was evaluated quantitatively and was shown to be limited by diffusion of Si through the silicide. For annealing in N2, the TiSi phase is stabilized compared to Ar annealing; additionally a titanium nitride forms near the surface and grows inward by another diffusion-limited process. When the TiSi and TiN reaction fronts approach the available Ti is consumed for these reactions; further silicide growth can only occur via complex phase transformations. The ratio of the activation energies for both diffusion processes was measured to be\(Q_{{\text{TiSi}}_{\text{2}} } /Q_{{\text{TiN}}} = 0.8 \pm 0.2\), in approximate agreement with literature data. The role of impurities for silicide growth will be discussed.