JPS572568A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the high frequency characteristics and the substrate withstand voltage of a semiconductor device by forming a high density region on the surface except the collector of a reversely conductive type buried layer around the periphery of the collector buried layer of triple diffused P-N-P transistor, thereby reducing the collector series resistance. CONSTITUTION:An N<->type buried layer 35 is formed on a (-) conductive type, e.g., P-type silicon substrate 36, and a P-N-P type transistor is formed thereat. High density N<+>type buried layers 43, 46 are formed on the periphery of the layer 35 and on an n-p-n type transistor forming region. Thereafter, a P<+>type isolation region 38 is formed in the same manner as the conventional one, a P type collector 33 is formed, and a P-N-P type transistor is formed, and an P-N-P type transistor is similarly formed. Since the layer 46 is thus formed, it can prevent the inversion of the layer 35 due to an automatic-doping phenomenon at the epitaxially growing time, and can enhance the collector and the substrate withstand voltages of the P-N-P type transistor. In addition, the collector series resistance can be reduced.