In this letter, we report on the high resolution patterning of a silicon surface without using a resist layer. A hydrogen passivated silicon surface is chemically modified by illumination with ultraviolet light (UV, &lgr;=350.7 nm) in air. Auger electron spectroscopy (AES) revealed that silicon oxide was formed at the illuminated areas. A light interference pattern was made on the silicon surface by two UV laser beams, oxidation occurred only at the maximum intensity, but not at the minimum. In this way oxide lines were fabricated with a width below 200 nm on a 500 nm period. The oxide lines were used as a wet etch mask to etch more than 25 nm into Si(110) without affecting the oxide. The advantage of this technique is that it is a very simple process which allows the high resolution patterning over large areas of silicon without using a resist. ©1995 American Institute of Physics.