PURPOSE: To provide a semiconductor device consisted of bipolar transistors with small occupying area by arranging a second conductive diffused layers at brim region and at down region of a trench as collectors and emitters, and by a thin insulating film of a trench side wall that functions as an insulation of a polysilicone layer that is connected with the collectors and emitters.

CONSTITUTION: A Locos oxide film 2 is formed on a first conductive N- substrate 1 and an insulating film 5 is formed on a formed side wall of a trench 4. After forming the second conductive diffused P+ layer at the region the emitters and the collectors are formed, a P+ polysilicone layer 9 is formed in the trench 4 and a first conductive diffused N- layer 11 is formed using a resist film 10 at the part where take-out diffusion of a base is formed. Then, an insulation layer 12 is formed, contacts are opened, metal wiring 13 are formed and PNP bipolar transistor with small occupying area are formed. With this, the semiconductor device consisting of the bipolar transistors with small occupying area is provided.