A sputtering rate near the silicon surface is different from that in the bulk during secondary ion mass spectrometry (SIMS) analysis. It is important to evaluate the sputtering rate change in the transient region in order to obtain the correct depth profile. In this study, we report the sputtering rate change in the transient region under various oxygen bombarding conditions. A sample measured was multiple BN delta layers separated by Si spacing layer. We used MRI analysis applied to SIMS profiles in order to determine the accurate delta positions. In concluding, when the incident angle is smaller than 278 in which SiO2 is formed, the sputtering rate at the surface is faster than that in the bulk and its difference becomes larger as the primary ion energy becomes larger. When the angle of incidence is 638, the native oxide at the surface makes the sputtering rate slightly slower than in the bulk. (C) 2008 Elsevier B.V. All rights reserved.