PURPOSE: To obtain a transistor having excellent surge resistance breakdown characteristics by approximately equalizing the impurity concentration of the con siderable section of a base region contacting with a collector region to the collector region.

CONSTITUTION: An N- epitaxial layer 12 in 1015/cm3 is formed onto P type Si 11 (an N+ layer is buried onto the base body 11 as necessary). A P- layer 13' having concentration in the same extent is shaped to the layer 12 in approximately 2μm depth, and an N- layer 12' in 1015/cm3 is deposited in approximately 5μm thickness. A P layer 13 is formed to the layer 12' on the layer 13' through diffusion, and an N+ layer 14 is diffused into the P layer 13 in approximately 3μm depth. According to this constitution, the base region is formed by the P- layer 13, which contacts with the collector layer and has the same concentration as the collector layer, and the P layer 13 having concentration required, the width of both layers is approximately 2μm respectively, and half base width is occupied precisely by the P- layer 13. According to this constitution, the lowering of the hFE of the transistor in a high current-density region is quickened, and the surge resistant breakdown characteristics are improved.