Real-time electric field drift experiments,in-situcapacitance-voltage profiling, deep-level transient spectroscopy and nuclear reaction analysis have been used to monitor hydrogen motion and passivation processes in silicon. Spontaneous hydrogen injection and very fast migration has been detected in the near-surface region of various Schottky barriers andp-njunctions. The effective hydrogen diffusivity is about 10−8cm2/s at 400 K in agreement with the estimated value obtained by extrapolation from the high-temperature diffusivity data. The results of real-timein-situmeasurements clearly demonstrate that the fast diffusing protons are involved in the hydrogenation processes of both shallow and deep levels. The possible physicochemical mechanisms for the observed spontaneous hydrogen injection which results in unintentional hydrogenation of the subsurface of silicon, and probably other semiconductors, are discussed.