In this paper, we report a DFB laser diode with a buried SiO2 grating. Epitaxy lateral overgrowth by metalorganic chemical vapour deposition (MOCVD) is conducted to grow the p-type InP cladding layers in the nano-patterned dielectric grating template. The large refractive index difference between SiO2 and InP results an index coupling coefficient κ of about 250 cm-1. The fabricated DFB laser showed a side mode suppression ratio larger than 45 dB measured. The technology developed can also be used for other applications that require high efficiency grating structure.