A field plate of a semiconductor device is provided with i) an insulating film that is formed on a surface of the semiconductor substrate, and includes a plurality of first regions, one for each of a plurality of FLR layers, that contact the layers and are arranged at intervals in a radial direction, and a plurality of second regions, one for each of the first regions, that are adjacent to the first regions in the radial direction, and ii) a plurality of first conductive films that are formed, one for each of the layers, inside of the insulating film, are arranged at intervals in the radial direction along the layers when a semiconductor substrate is viewed from above, and that are electrically connected to the layers. A thickness of at least a portion of the second regions is thicker than a thickness of the first regions.