When analyzing insulating films on silicon substrates by quadrupole SIMS instruments, large variations in secondary ion intensity near the interface often occur. In this paper, we investigated these phenomena by analyzing silicon-nitride films deposited by chemical vapor deposition (CVD) at different conditions. It has been found that these variations are caused by a change in the energy distribution due to the insulating properties of the films. Further, the observed SIMS behavior seems to be related to the breakdown field strength of the insulating films. (C) 2004 Published by Elsevier B.V.