| 摘要 |
PURPOSE:To form an active base region of a narrow width and a high impurity concentration without the increase in the surface impurity concentration of this region, and to further increase the cut-off frequency fT by a method wherein a base region is formed by impurity ion implantation through a thin polycrystalline Si layer of a minimum thickness necessary to prevent the damage at the time of ion implantation. CONSTITUTION:The first polycrystalline Si layer 19 of a required thickness is formed in the main surface of a semiconductor substrate by CVD. Next, B<+> is ion-implanted to the surface of a base-forming region 17 through a polycrystalline Si layer 19. Then, a P type base region 20 is formed by annealing treatment. The second polycrystalline Si layer 21 is formed on the layer 19, and Si nitride film patterns 22a and 22b are formed on this layer 21. The layers 19 and 21 are selectively oxidized with this Si3N4 film as a mask by the method of high-tension oxidation, and an SiO2 passivation film 23 is formed. As<+> is ion-implanted to the surface of the base region 20. A resist film 25 is removed, and an N<+> type emitter region 26 is formed. Finally, a bi-polar transistor completes by formation an emitter wiring 27a, a surface protection insulation film, etc. |
