A bombardment of energetic particles such as secondary electrons and recoiled ions ejected from the target plane is a very useful technique for modifying the structure of the film in reactive sputtering. It leads to interesting effects such as enhancement of reactivity, adatom mobility, and atomic peening. Therefore, the state on the surface of the as-deposited film may significantly depend on the bombardment condition. So, in this study, the relationship between the bombardment condition and the surface morphology of TiO2 films has been investigated in detail. TiO2 films with a thickness of about 0.8 - 2.3 mum were deposited by dc reactive sputtering on glass-slide substrates. The surface roughness of films was measured with atomic-force microscopy. The roughness parameter Ra on the surface of TiO2 films depended on the energy and the number of bombarding particles. After increasing the energy and the number of bombarding particles, Ra increased from 10 to 77 nm. Consequently, it was found that the surface morphology of TiO2 films strongly affected the plasma exposure to the growing film.