There are provided a semiconductor device that includes a bypass protection unit against surge voltage or the like, achieves good withstand voltage characteristics and low on-resistance (low On-state voltage), has a simple structure, and is used for large-current purpose and a method for producing the semiconductor device.In the present invention, the semiconductor device includes an n+-type GaN substrate 1 having a GaN layer that is in ohmic contact with a supporting substrate, a FET having an n−-type GaN drift layer 2 in a first region R1, and an SBD having an anode electrode in a second region R2, the anode electrode being in Schottky contact with the n−-type GaN drift layer 2. The FET and the SBD are arranged in parallel. A drain electrode D of the FET and a cathode electrode C of the SBD are formed on the back of the n+-type GaN substrate 1.