A method of manufacturing a semiconductor device includes preparing a layer, including columns, the columns extend a first direction parallel to the surface of the layer, the columns are arranged at intervals, interdigitally sandwiching other columns so as to implement a superjunction structure so the columns and the other columns are side by side; forming well regions in the layer; forming source regions in the well regions; forming an insulating film on the well regions; and forming gate electrodes on the gate insulating film, the gate electrodes bridging corresponding source regions in neighboring well regions, a temperature detection diode at an area in the gate electrodes, one column has a first width in a second direction, the temperature detection diode has a second width in the second direction, and the first width equal to the second width, and the second direction is perpendicular to the first direction.