Effects of ionized cluster beam (ICB) bombardment on film formation process have been studied in order to understand the unique properties of films grown by this method. By combining the results from cluster size distribution measurements. STM imaging of the initial stages of deposition, and the grown film characteristics, the principal features of ICB is elucidated and the differences between ICB deposition and MBE are clarified. By using a newly developed gas cluster beam system, preliminary results of surface bombarding effect have been obtained.