A reduction in the scale of semiconducting devices has created many challenges in SIMS depth profiling. With fewer and shallower dopant atoms, depth resolutions have had to improve significantly especially in the first few nanometres. It is widely accepted that by using lower primary ion beam energies to minimise transient widths and beam induced mixing that the depth resolution can be optimized. The development of the Floating Low-energy Ion Gun (FLIG) has enabled SIMS to operate with beam energies in sub-keV regions enabling depth pro. ling of shallow features. Accurate depth pro. ling also relies on accurate depth calibration. Typically depth calibration is performed by measuring SIMS crater depths and assuming a constant sputter rate thus incurring an error. TEM analysis in conjunction with SIMS has successfully been used to depth calibrate a test structure with an error <0.5 nm. The top 5 nm of a surface is a problematic region for SIMS depth pro. ling due to depth calibrations issues. The current work is to obtain an accurate depth profile of a 5 nm thick altered layer using TEM to assist depth calibration. With the depth resolution being dependent on the altered layer, the analysis of sub-keV altered layers will give an insight into the ultimate depth resolution attainable. (C) 2008 Elsevier B.V. All rights reserved.