Annealing ofSiO2/(100)Siinterfaces in hydrogen in the temperature range of 500–800 °C is found to introduce a considerable density of fixed positive charge. The charge is diamagnetic, and shows no correlation with any kind of dangling bond defects at the Si surface or in the oxide. The observed charged state is attributed to hydrogen bonding to a bridging oxygen atom at the interface (threefold coordinated oxygen center), which may account for the well-known oxidation-induced charge at theSi/SiO2interfaces. ©1998 American Institute of Physics.