formed in steady state representing the "worst case". It would be an advantage of modeling to obtain extrapolation from steady state experiments to real dynamic operation. Additionally, it has been remarked for long that most devices can recover to some extent if operated in the proper biasing. This situation has been first noted for MOS threshold voltage, silicon-on-sapphire leakage [Srou-76] currents and parasitic MOS edge leakage currents. This has been understood as the neutralization of trapped holes by electron currents, which can be enhanced if bias is made evolving towards a larger overlap of electron current flooding the trapped holes area. Consequences have been studied in details in [Flee-90], who called this effect "Radiation-Induced Charge Neutralization" (RICN), thus affecting Vot. By taking into account the fact that the interface states are basically not affected by this electron flooding, [Flee-90] took advantage of the separation into two components V ot and Vit to propose "Twelve Rules", presented nearly as theorems, to serve as guidelines to predict the behavior of a given MOS under switched bias condition, on a purely experimental basis and without invoking any calculation. However, analytical treatment of switched bias is possible [Lera-89a p. 83 and Lera-89b]. In this course, numerical modeling is exemplified by considering successively trapping at the interface and trapping in the volume. In the example given in fig. 43 to 48, a 300 nm oxide is studied with CEA-TRAPPOX" R v.4, as representing a Field Oxide (parameters given in the Appendix) [Lera-99b]. The bias is switched from +5 to -5 V within 0.1 second at 2.5 seconds after the beginning of irradiation (i.e. at 2.5 kilorad(SiO2). In a first set of calculations, we consider the case of a distribution of traps located in the first 30 nm on the silicon side. One clearly sees a "recovery" due to the neutralization of the trapped charge by the electron flux when the bias is reversed from +5 to -5 V. Vot (Volts) Voltage at mid-oxide (Volts) F