Method of fabricating semiconductor device

A method of fabricating a semiconductor device including an NPN transistor and a PNP transistor, comprising the steps of:

• forming a well region in a predetermined region in a semiconductor substrate of a first conduction type, the well region being of a second conduction type;
• forming a base diffusion layer of the first conduction type in the well region;
• forming a base diffusion layer of the second conduction type in a predetermined region in the semiconductor substrate;
• forming a first polycrystalline silicon film (115) on the semiconductor substrate;
• introducing impurity corresponding to a first conduction type into a portion of the first polycrystalline silicon film (115) which extends above an NPN-transistor-forming region;
• introducing impurity corresponding to a second conduction type into a portion of the first polycrystalline silicon film (115) which extends above a PNP-transistor-forming region;
• forming a first insulating film (7) on the first polycrystalline silicon film;
• etching the first insulating film and the first polycrystalline silicon film, and simultaneously forming emitter lead-out electrodes (9, 117) and collector lead-out electrodes (10, 118) in regions above emitter-contact-forming regions and collector-contact-forming regions of the NPN transistor and the PNP transistor;
• forming second insulating films (11, 12) at sides of the emitter and collector lead-out electrodes;
• simultaneously forming base contacts (101, 104) of the NPN transistor and the PNP transistor;
• forming a second polycrystalline silicon film (119) on the semiconductor substrate;
• introducing impurity corresponding to the second conduction type into a portion of the second polycrystalline silicon film (119) which extends above the NPN-transistor-forming region;
• introducing impurity corresponding to the first conduction type into a portion of the second polycrystalline silicon film (119) which extends above the PNP-transistor-forming region;
• etching the second polycrystalline silicon film to form a base lead-out electrode (13) of the NPN transistor and a base lead-out electrode (120) of the PNP transistor, wherein the base lead-out electrode of the NPN transistor includes impurity corresponding to the second conduction type, and wherein the base lead-out electrode of the PNP transistor includes impurity corresponding to the first conduction type;
• diffusing the impurity from the emitter lead-out electrode, the collector lead-out electrode, and the base lead-out electrode to form emitter diffusion layers (15, 121), collector contact diffusion layers (17, 123), and base contact diffusion layers (16, 122) of the NPN transistor and the PNP transistor;
• locating an end of the emitter diffusion layer (15, 121) and a first end of the base contact diffusion layer (16, 122) at positions directly below a portion of the second insulating films (11, 12) which extends at a side of the emitter lead-out electrode (9, 117) in each of the NPN transistor and the PNP transistor;
• and
• locating a second end of the base contact diffusion layer (16, 122) and an end of the collector contact diffusion layer (17, 123) at positions directly below a portion of the second insulating films (11, 12) which extends at a side of the collector lead-out electrode (10, 118) in each of the NPN transistor and the PNP transistor.