High quality Au/CaF2/n-Si(111) metal-insulator-semiconductor structures with thin (<2.5 nm) epitaxial fluorite layers were fabricated. Damage of such structures due to electrical overload has been investigated in this work. Current-voltage characteristics of these structures before and in process of degradation are measured. A mechanism explaining the pronounced breakdown at reverse bias is suggested. This mechanism relies on the potentially possible bistability arising from the one-band character of tunneling in the studied devices. Some comparisons with the degradation scenario in SiO2-based samples are made. Wear-out fields for CaF2 films are estimated. The changes in behaviour of fresh and damaged structures under visible light irradiation are treated. (C) 2008 Elsevier B.V. All rights reserved.