PURPOSE: To form a Schottky diode together with a bipola transistor on a semiconductor substrate so as to improve a device in integration by a method wherein a polycrystalline silicon pattern, which is necessary for the formation of a graphed base, formed of a polycrystalline silicon film is employed.

CONSTITUTION: A second conductivity type impurity is injected into a first and a second polycrystalline silicon patterns 105a and 105b through ion implantation, the second conductivity type impurity is injected self-alignedly into a first conductivity type semiconductor layer through the first polycrystalline silicon pattern 105a serving as a mask so as to form a guard ring 104 of a Schottky diode. Therefore, when an active region and a contact of a bipolar transistor of high performance are formed self-alignedly with a polycrystalline silicon film, a Schottky diode with a guard ring can be build without adding a special masking process. By these processes, high performance and high level of integration of a semiconductor device can be promoted.