This semiconductor device includes a first device and a second device provided on a semiconductor substrate and having different breakdown voltages. More specifically, the semiconductor device includes a semiconductor substrate, a first region defined on the semiconductor substrate and having a first device formation region isolated by a device isolation portion formed by filling an insulator in a trench formed in the semiconductor substrate, a first device provided in the first device formation region, a second region defined on the semiconductor substrate separately from the first region and having a second device formation region, and a second device provided in the second device formation region and having a higher breakdown voltage than the first device, the second device having a drift drain structure in which a LOCOS oxide film thicker than a gate insulation film thereof is disposed at an edge of a gate electrode thereof.