| 摘要 |
PURPOSE:To reduce the capacity of base-collector junction and to increase operation speed by a method wherein the lower end of a base region and the upper ends of channel stopper regions are placed in the same plane which is perpendicular to a substrate and are selfmatchingly isolated. CONSTITUTION:When dielectric isolation bands between elements 23 are formed on a semiconductor substrate 24, selective oxidation is performed twice. Namely, after performing the first oxidation by using an Si3N4 film etched to a desired shape as an oxide shielding film, the predetermined region of a generated SiO2 film is removed and impurities are diffused to form channel stoppers 22. Then, the second oxidation is performed by using the same Si3N4 film as the first Si3N4 film to flatten the surface of the substrate and to form thick dielectric isolation bands 23 as well. After that, the unnecessary Si3N4 film is removed to form a base region 21 by diffusion. When the second oxidation is performed, a low temperature of 950 deg.C is adopted to increase lateral oxidation speed more than the impurity diffusion speed of the stoppers and to locate the upper ends of the stoppers 22 at a lower position than the end sections of the isolation bands 23. Then, the lower end of the base 21 and the upper ends of the stoppers 22 are selfmatchingly isolated. |
