We developed a new sample preparation method for thick insulating samples in secondary ion mass spectrometry (SIMS) analyses. In power semiconductor devices, impurity analyses in passivation layers and sealing resins are very important. SIMS analyses are suitable for this purpose, but in SIMS analysis of insulating samples, charging up would be a serious problem. Previous methods are not efficient enough to avoid the charging up of thick insulating sample, such as passivation layers. In this new technique of sample preparation, we made trenches by a FIB Ga beam, and filled them up with Pt. Including these Pt lines into the raster area, the charge of the sample can flow away through these lines during SIMS analysis. We applied this method to SiN/Si samples and confirmed that embedded Pt lines were effective for preventing the charging up. (C) 2002 Elsevier Science B.V. All rights reserved.