Porous silicon, produced by the anodic oxidation of p-type single crystal wafers of silicon in hydrofluoric acid/ethanol electrolytes has been subjected to rapid thermal oxidation. For comparison purposes, and also to generate porous oxide for subsequent nitriding, other samples of porous silicon were subjected to conventional furnace oxidation. By TEM, EDS, and ESCA it was shown that the structures and compositions of the oxides produced by the two routes were similar. It was further demonstrated that oxidized porous silicon could be nitrided by rapid thermal processing. The resulting structure, although still porous, showed a much diminished etching rate in hydrofluoric acid, compared to the original oxide.