This paper presents a discussion on internal stress generation in CoSi2 films formed by rapid thermal annealing (700-900 degrees C). The internal stress is measured by X-ray diffractometry. The internal stress is 1.1-1.3 GPa, and is almost independent of the annealing temperature. This is in contrast with the fact that the internal stress of TiSi2 films increases with the annealing temperature. This contrast is attributed to the fact that thermal stress of CoSi2 films relaxes during cooling, while in TiSi2 films the thermal stress contributes to the internal stress without relaxing.