Abstract: Two bipolar transistors formed on a common semiconductor substrate are separated by a separation band. The separation band includes a first separation portion having the same conductivity type, and substantially the same impurity concentration and diffusion depth as those of each of base regions of the bipolar transistors, and second separation portions, formed on both sides of the first separation portion, which have the same conductivity type and substantially the same impurity concentration and diffusion depth as those of each of emitter regions. The second separation portions are formed so as to be shallower than the first separation portion. The second separation portions are formed across the first separation portion in a deeper portion of the substrate and a collector region. The second separation portions enclose the respective transistors, and the first separation portion separates the transistors from each other.