The effects of hot-carriers during the off-state operation of 0.15µm Low Dose SIMOX Partially Depleted MOSFETs are investigated. A correlation between the ageing characteristics of the MOSFETs and the created defects is presented. The front channel degradation is strongly affected by the back gate bias. This is due to parasitic bipolar transistor. However, the degradation mechanisms of both channels are different. Deep Level Transient Spectroscopy was used for defect evaluation in both channels and interfaces: the front and the back. In depth studies, showed that during the stress two different kinds of defects are created: electron traps similar to those induced after ion implantation of Si and hole traps similar to those induced after electron irradiation of Si.