A semiconductor device (100) according to the present invention comprises a vertical PNP bipolar transistor (20), an NMOS transistor (50) and a PMOS transistor (60) that are of high dielectric strength, and a P-type semiconductor substrate 1, as shown in FIG. 2. A substrate isolation layer (21) of the PNP bipolar transistor (20), a drain buried layer (51) of the NMOS transistor (50), and a back gate buried layer (61) of the PMOS transistor (60) are formed simultaneously by selectively implanting N-type impurities, such as phosphorous, in the semiconductor substrate (1). This invention greatly contributes to curtailing the processes of fabricating BiCMOS ICs and the like including vertical bipolar transistors with easily controllable performance characteristics, such as a current amplification factor, and MOS transistors with high dielectric strength and makes even more miniaturization of such ICs achievable.