In this study, RMS roughness values of the interface between top silicon and buried layer in SIMOX-SOI SIMOX, separation by implantation of oxygen; SOL silicon-on-insulator were directly measured by AFM. The results revealed that they were self-affine fractal, Based on the variation of the RMS values with scan sizes, the fractal dimensions and horizontal cutoffs of the fractal interfaces were calculated. It was found that the cutoff values varied with the different processes suggesting that the cutoff is sensitive to process and can be used to characterize the quality of SIMOX-SOI wafer. (C) 2002 Elsevier Science B.V. All rights reserved.