A two-dimensional secondary ion mass spectrometry dopant profiling technique, using a specially prepared sample, has been used to provide high spatial resolution, high sensitivity, dopant maps of boron and arsenic. These have been compared with TSUPREM(IV) simulations. However, investigation of the disagreements between the modeled and experimental data cannot be made, as a major problem has been accurately determining the position of the mask edge on the reconstructed profile. Previous methods have introduced errors of up to 0.2 mum. This has been overcome by using a low energy, low dose, germanium implant as a marker of the mask window. The effect of this marker implant on the dopant distribution to be measured has been investigated and estimates of the accuracy of locating the mask edge have been made using the TSUPREM(IV) code. It is expected that the mask edge in later profiles will be located to better than 15 nm.