A substantial reduction of leakage currents during voltage sweeps from 0 to+20 Vis observed for overlap capacitors with polycrystalline silicon (polysilicon) capacitor plates and thermalSiO2as an insulator. The responsible electrical passivation has a high thermal stability and is localized at the sharp corner, where the upper polysilicon wraps over (overlaps) the lower polysilicon. From baking and recycling electrical-sweep experiments, we conclude that: (1) stability of the localized electrical passivation comes from electrons trapped at deep neutral oxide traps, (2) more than one trap binding energy is involved, and (3) thermal activation energies for electron detrapping, with estimated magnitudes up to 1.3 eV, are about three times larger than previously reported. ©1997 American Institute of Physics.