An important issue in semiconductor device operation is the rate at which current or voltage stress creates defects that can eventually degrade device operation. Based on recent results on nitrided gate dielectrics, we have concluded that bonded-H at the Si-SiO2 interface plays a role in the formation of metastable defects that can be activated, and subsequently neutralized, by sequential trapping of injected holes and electrons. In this article, differences in defect behavior for Si-SiO2 interfaces that have been exposed to nitrogen (N-) atoms or N-H groups are discussed. Based on these results, a microscopic model for interfacial defects is proposed.