The effect of impurity on the thermal stability of titanium silicide (TiSi2)/single‐crystal silicon (Si) structures has been studied. It is found that nitrogen and oxygen in the TiSi2film significantly influence the morphological changes of a TiSi2/Si structure during high‐temperature annealing at 1100 °C for 2–20 s. Nitrogen impurity improves the thermal stability of the TiSi2/Si structure, whereas oxygen degrades it.