This paper describes a study of the rapid thermal processing of Ti thin films on SiO2 in Ar and N2 in the temperature range 400–1100 °C. The resulting layer structures were analyzed by means of Rutherford backscattering spectrometry and elastic recoil detection. The latter technique yielded quantitative information with a low detection limit of the depth distribution of H, O, and N. The underlying SiO2 film starts to react with the Ti at 500 °C. Oxygen originating from the reduction of SiO2 is dissolved in the Ti layer. As long as the solubility limit of O in Ti is not reached, nitridation of the Ti in the surface region causes O to be snow‐plowed out of the top surface layers. The reaction of Ti with SiO2 is characterized by an activation energy of 0.7 eV. For the case of rapid thermal processing in N2, the evolution of the layer structure is governed by a competition between nitridation and the above‐mentioned oxidation of Ti. In between the Ti oxide and the remaining SiO2, a silicide of probable composition Ti5Si3 is formed.