When niechanically polished Ge, Si, GaAs, LiNbOj, Cd-Ga-garnet, fused quartz and glass surfaces are sputtered by low energy ion beam (from 300 to 1200 eV) at an incident angle of 45°, the surfaces are found to exhibit hillock-like features. The influence of ion beam incident angle, energy, dose and target rotation on surface topography have been investigated. The analysesof hillocks by SIMS and AES show that their formation may not be due to impurity contamination caused by redeposition. A mechanism for hillock formation is proposed. This can be expressed by aformula, through which all the results can be successfully explained.