The resonant broadening Γ of trap assisted tunneling in metal-insulator-semiconductor structures has been analysed in the framework of the stationary resonance model and an analytical expression for Γ has been obtained from the Green function of the barrier in a two-band model. Experimental results on AlSiO2Si(n) structures are reported, showing a deviation from the ideal Shockley dependence. A possible explanation of this phenomenon is bassed on a saturation process due to the trapped charge in the insulator. By means of the forward saturation current and the tunneling time associated to the resonant broadening, the trap density in the oxide is obtained. © 1985.