The step-terrace structures at the interface between the Si layer and the buried SiO2 layer of a Separation by IMplanted OXygen substrate has been observed by using atomic force microscopy (AFM) after removing the SiO2, and Si layers. The time evolution of the Si-SiO2 interface roughness during high-temperature annealing was analyzed by the scaling analysis of AFM data. The correlation length exhibited a nice correspondence to the size of square domain structures. Decreasing in the index of the length scale indicates that the growth mechanism changes as the annealing proceeds. (C) 2002 Published by Elsevier Science B.V.