For the p-Si, n-Si and n/p(+)-Si MOS tunnel diodes with a sub-3 nm insulator layer, the interrelation between oxide degradation, changes in current-voltage curves and changes in the luminescence spectra, is experimentally studied. The evolution of the spectra is associated with the changes in carrier transport through the SiO2 and consists in a suppression of the high-energetic radiation. In some devices (n-Si), the post-stress redistribution of applied voltage within a MOS structure as a whole, was observed. In the perspective, screening the measured luminescence spectrum with the reference spectrum simulated for an undamaged structure, conclusions can be made as to whether the oxide layer is in order or degraded. (C) 2003 Elsevier Ltd. All rights reserved.