| 摘要 |
PURPOSE:To prevent the damage of an element on the application of overvoltage by making a discrimination between the values of breakover voltage and avalanche voltage and forming circuit constitution in which voltage applied to the element is brought to a rated value in the opposite direction or avalanche voltage or lower. CONSTITUTION:A P-base 3 consisting of a second semiconductor layer is shaped onto a P-emitter 1 through an N-base 2, and an N-emitter 4 composed of a first semiconductor layer is formed into the P-base 3 in predetermined diffusion depth. A recessed section 5 is shaped on a bottom in the second semiconductor layer, a P-N junction 6 having a curvature smaller than the recessed section 5 is formed between the second semiconductor layer and a third semiconductor layer, a surface electrode 7 is shaped onto the P-base 3 on the main surface side, and a back electrode 8 is formed to the P-emitter 1 on the back side. Since the field strength of a curved section in the P-N junction 6 is larger than other sections in such a thyristor having an overvoltage protective function, voltage breakdown is generated in the section. Accordingly, the generation of a damage to an element on the application of overvoltage is prevented. |
