Silicon-compatible micromachining provides a foul cost monolithic solution for the integration of microelectromechanical systems (MEMS). In the lest years, CMP (the French MultiProject Wafer Service) has made available technological solutions for the fabrication of CMOS-compatible MEMS. Numerous monolithic devices have been fabricated wing this service. The inspection of failed devices has allowed the identification of the most typical failure mechanisms and design errors for this type of MEMS. This valuable information, together with a detailed analysis of the fabrication processes, is used in this paper to provide a classification of faults in silicon-compatible MEMS which can later be used for fault simulation and testing.