An npn transistor allowing the potential of each terminal to be easily set and superior in characteristics such as withstand-voltage performance and current amplification factor can be obtained. An n-type buried layer on a p-type substrate, a p-type buried layer on the n-type buried layer, n-type epitaxial layers covering the above layers, terminal regions on the surfaces of the layers, p-type outer-periphery layers encircling the terminal regions, and an encirclement layer encircling the layers are included, and p-type base regions and the p-type outer-periphery layer are continued to the p-type buried layer to separate a collector region from a p-type substrate and the n-type buried layer and the n-type encirclement layer are continued to separate the p-type buried layer, the p-type base region, and the p-type outer-periphery layer from the p-type substrate.