JPS564272A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a transistor which has low noise and high amplification characteristics by diffusing a base region in a semiconductor substrate with an oxide film as a mask, removing the surface layer of the base region containing lowered impurity density when forming an emitter region in the base region and forming the emitter region therein. CONSTITUTION:An n<+>-type layer 7 becoming a collector region is diffused in the back surface of an n<->-type Si substrate 1, and a p-type impurity is deposited on the surface of the substrate 1 with an oxide film 8 having an opening as a mask. When it is then extention diffused to form a p-type base region 2 therein, impurity is partly absorbed into the film 8 to lower the density on the surface of the region 2. Therefore, an opening is perforated at the oxide film 8' thus produced to etch it so as to form a recess in the region 2, and an oxide film 8'' is again coated thereon so that the recess becomes peak density. Thereafter, an opening 10 is again perforated at the film 8'', an n<+>-type emitter region 3 is diffused corresponding to the peak position, and electrodes 11-13 are then mounted on the respective regions.