The anodic oxidation of silicon in a 0.04 N solution of potassium nitrate in ethylene glycol with small amounts of water is a hole consuming process. Therefore, n-type silicon, anodically biased, behaves in the dark in many respects as a reverse biased diode. Under steady-state conditions a certain, in general a very low electrochemical reaction rate is established. If the sample is locally implanted with ions or locally illuminated the ion implanted or illuminated regions can serve as an additional source of minority carriers and show a faster oxidation rate than the nonimplanted or nonilluminated areas. The influence of radiation damage as well as of a focused laser beam (radius 4 mum) on the local oxidation of anodically biased n-type silicon is discussed. The electrophysical properties of the silicon/anodic oxide interface are investigated by forming Metal/Oxide/Semiconductor (MOS) structures.