When a semiconductor substrate of a semiconductor device is viewed from above, an isolation region, an IGBT region, and a diode region are all formed adjacent to each other. A deep region that is connected to a body region and an anode region is formed in the isolation region. A drift region is formed extending across the isolation region, the IGBT region, and the diode region, inside the semiconductor substrate. A collector region that extends across the isolation region, the IGBT region and the diode region, and a cathode region positioned in the diode region, are formed in a region exposed on a lower surface of the semiconductor substrate. A boundary between the collector region and the cathode region is in the diode region, in a cross-section that cuts across a boundary between the isolation region and the diode region, and divides the isolation region and the diode region. The collector region formed in the isolation region has a higher dopant impurity concentration than the collector region in the IGBT region.