An integrated injection logic semiconductor device is composed of an N type semiconductor substrate, a P type layer, a first N type region so formed as to penetrate through the P type semiconductor layer and contact the N type semiconductor substrate, a second N type region formed in the P type semiconductor layer, and a P type region formed in the first N type region. A third N type region is provided surrounding said first and second N type regions and penetrating through the P type semiconductor layer. I.sup.2 L circuit is composed of a lateral PNP transistor whose emitter, base and collector are constituted by said P type region, said first N type region and said P type semiconductor layer, respectively, and a vertical NPN transistor whose emitter, base and collector are constituted by said N type semiconductor substrate, said P type semiconductor layer and said second N type region, respectively.