A novel technique has been developed to fabricate surface-relief gratings using photosensitive gel films. Gel films which were derived from metal-alkoxides chemically modified with P-diketones were photosensitive owing to remaining chelate rings; the W-irradiation of these gel films substantially decreased their solubility in acidic aqueous solutions or organic solvents. Leaching of the gel films after UV-irradiation through a mask and subsequent heat-treatment gave negative patterns of the mask used. Fine-patterns of PLZT films, as well as Al2O3, ZrO2, and TiO2 films, were successfully formed by the above process. Utilizing this process, surface-relief gratings were fabricated on silica glass and Si substrates by the irradiation of the modified gel films with a XeF excimer laser through a phase mask. Very uniform diffraction gratings with a pitch of about 1.0 mu m were produced for Al2O3, ZrO2, and TiO2 films, along with PLZT films. The morphology and diffraction efficiency of the gratings obtained were examined in terms of fabrication conditions.