The present invention provides a substrate for a semiconductor device and a semiconductor device using the same. The substrate for a semiconductor device comprises a ceramic supporting base plate formed by a polycrystalline aluminum nitride (AlN) sintered body; at least one silicon oxide layer formed on the base plate by a sol-gel method wherein the at least one silicon oxide layer has an average roughness less than the base plate to block polycrystalline orientation of the base plate and has a total thickness in a range of 10˜5000 nm, the silicon oxide layer is only formed from the sol-gel method and is not single crystalline; a first buffer layer comprising aluminum nitride (AlN) on the at least one silicon oxide layer with a thickness of 0.1˜10 μm; and a gallium nitride layer formed on the first buffer layer and having a single-crystal crystalline structure.