Multilevel structures in sol-gel thin films with a single step process are demonstrated. A negative-tone hybrid sol-gel material is UV-exposed through a gray-scale calibration mask. Test strips of different depths and a continuous test profile are demonstrated. A maximum depth difference exceeding 1.5 μm is obtained, which permits the fabrication of multilevel diffractive elements for use in visible light. This method of using sol-gel material with a gray-scale mask has the potential for low-cost fabrication of complex multilevel micro-optical structures.