PURPOSE: To reduce an active region, and enable the contraction of a device, by forming, in a self-alignment manner, a protrusion type active region in the selection region on a substrate, and leading out an electrode from the sidewall of said region.
CONSTITUTION: On an n-type Si substrate 31, the following are formed in order; an SiO 2 film 32, an SiN film 33, a poly Si film 34 and an SiO 2 film 35. In the SiN film 33, an cavity part 38 is formed, and the SiO 2 film 32 is closed after the poly Si film 34 is filled in the cavity. After an SiN film 39 is formed on the inner wall of an aperture part 36, an epitaxial layer 40 is selectively formed. After the SiN film 39 is eliminated, the peripheral part of the layer 40 is filled with a poly Si film 41. By thermally oxidizing the poly Si film 41, an SiO 2 film 43 is formed. At the same time, an external base diffusion layer 42 of p-type is formed in the self-alignment manner. An aperture is made on the SiO 2 film 43 for forming an internal base diffusion layer 45, and a poly Si film 46 is formed on the whole surface to form an n + emitter diffusion layer 48. Finally, an emitter electrode 49, a collector electrode and a base electrode (not shown in figure) are formed.