In a vertical semiconductor device including a first base layer of a first conductivity type, second base layers of a second conductivity type, emitter layer of the first conductive type and gate electrodes which are formed at one main surface of the first base layer and including a buffer layer of the first conductivity type, a collector layer of the second conductivity type and a collector electrode which are formed at the other main surface of the first base layer, an electric field relaxing structure selectively formed outside from the second base layers and the collector layer is formed expect the region below the electric field relaxing structure.