Periodic structures consisting of Ge nanoparticles were formed in buried channel waveguides. Such periodic structures were created in GeO(2)-B(2)O(3)-SiO(2) thin glass films by the combination of exposure to interference patterns of ultraviolet laser light and thermally induced phase changes of the glasses. The periodic structures in the channels served as the Bragg gratings with high diffraction efficiencies in the optical communication wavelength. Transmission spectra measurements show the depths and positions of the diffraction peaks as 37.77 dB at 1536.2 nm and 38.72 dB at 1537.6 nm, respectively, for TE-like and TM-like modes. The diffraction efficiencies remain unchanged even after further annealing at temperatures as high as 500 degrees C.