We report high-Q sol-gel microresonators on silicon chips, fabricated directly from a sol-gel layer deposited onto a silicon substrate. Quality factors as high as 2.5ϫ 10 7 at 1561 nm were obtained in toroidal microcavities formed of silica sol-gel, which allowed Raman lasing at absorbed pump powers below 1 mW. Additionally, Er 3+ -doped microlasers were fabricated from Er 3+ -doped sol-gel layers with control of the laser dynamics possible by varying the erbium concentration of the starting sol-gel material. Continuous lasing with a threshold of 660 nW for erbium-doped microlaser was also obtained. Recently, a chip-based silica resonator structure in the form of a microtoroid has demonstrated ultrahigh-Q-factors in the range of 100 million. 1 By coating these high-Q microcavities with erbium-doped sol-gel films 2 or by beginning with erbium implanted silica layers, 3 low threshold rareearth-doped microlasers on-a-chip have been demonstrated. In another study, the realization of integrated Raman microlasers beginning with a layer of thermally-grown silica has been achieved. 4 Microlasers on silicon chips are especially interesting because they are integrable with other optical or electric components. In this work, we demonstrate the possibility of making microlasers directly from the sol-gel layers on the silicon wafer. The sol-gel method for preparing silica and silicate from a metal alkoxide precursor provides a versatile and cost-effective way to fabricate various components on silicon chips. It combines control of composition and microstructure at the molecular level with the ability to shape materials in bulk, fiber, powder, and thin film forms. 5 This technique allows a wide variety of thin films to be deposited on various substrates. In addition, optical devices, including buried-channel erbium-doped waveguide amplifiers, microlenses, one-dimensional photonic crystal devices and external-cavity distributed Bragg reflector ͑DBR͒ laser have been achieved using the sol-gel method. 6-9 Here we report a new method to fabricate both erbium-doped microlasers and Raman microlasers on a silicon chip using sol-gel films as the base material for microtoroid formation. In one series of experiments, erbium-doped sol-gel films are used to create low threshold microlasers. In a second set of experiments, pure silica sol-gel layers are processed into ultrahigh-Q Raman microlasers. Both of these cases demonstrate the ability to use spin coating of sol-gel films as a processing alternative to deposition or oxidation methods for silica layer formation.The sol-gel solution was prepared by hydrolyzing tetraethoxysilane ͑TEOS͒ using water with the molar ratio of water to TEOS around 1-2. Hydrochloric acid was added to make the solution in acid condition. Er 3+ ions were introduced by adding Er͑NO͒ 3 to achieve the desired Er 3+ concentration. After reaction at 70°C for 3 h, a viscous solution was formed. The silica sol-gel film was then deposited on a silicon substrate by the spin-coating method. Different thicknesses of the s...