The buried oxide of wafer-bonded silicon-on-insulator (SOI) materials was degraded by means of charge carrier injection into the oxide. Both Fowler-Nordheim injections using oxide fields above 7 MV/cm and ultraviolet (UV) photoinjections were made. The injections were made using metal-oxide-semiconductor (MOS) capacitors formed after a complete removal of the silicon film. As a result of photoinjection the oxides of capacitors with bonded SiO2/SiO2 interfaces were charged resulting in a 0.3 V shift in the flatband voltage. For this group of capacitors Fowler-Nordheim injection resulted in a strong positive charging of the oxide as well as in an increase of Si/SiO2 interface states. Capacitors with bonded Si/SiO2 interfaces were found to be less degraded as a result of the charge injection as compared to capacitors with bonded SiO2/SiO2 interfaces. Secondary ion mass spectroscopy (SIMS) revealed a pronounced hydrogen peak at the bonded SiO2/SiO2 interface. The results from the electrical and the SIMS investigations indicate that a bonded SiO2/SiO2 interface is a highly defective region affecting the performance of the MOS system.