In this paper, a combined random telegraph signal (RTS) and low-frequency (LF) noise study is applied to partially depleted (PD) metal-oxide-semiconductor transistors (MOST's) processed on SIMOX substrates. As will be demonstrated, the LF noise behaviour is determined both by the front-oxide/interface quality and by the defectiveness of the thin Si film. Kink-related excess noise is caused by generation-recombination (GR) events, taking place at defects in the film and giving rise to a Lorentzian spectrum. The amplitude of the corresponding noise peak is proportional to the defect density, allowing silicon-on-insulator (SOI) materials' characterization. Furthermore, quite often RTS's are observed, which are thought to be related to GR centres in the film. The RTS features lend themselves to spectroscopic analysis, provided an accurate device model is available. These methods are applied to investigate the role of the gate-oxidation temperature and the isolation technology on the noise behaviour of 1 mum SOI CMOS transistors.