We report the effects of isothermal annealing on the current component, the paramagnetic K-0 centers, and charge accumulation, induced by exposing silicon nitride films and silicon nitride-silicon dioxide double-layer films to 4.9-eV ultraviolet (UV) illumination. The UV-induced current component decayed as a result of the isothermal annealing at temperatures ranging from 27 degrees C to 240 degrees C, and was induced once again by UV exposure following the annealing. The density of the current component showed a close correlation with the density of the K-0 centers. Based on detailed analysis, we show that electron-hole pair generation in the bulk of the silicon nitride film is the possible source of the UV-induced current component. (C) 2013 Elsevier B.V. All rights reserved.