| 摘要 |
<p>PURPOSE:To enable formation of a transistor without affecting characteristics of other element by forming an N-type buried layer in a P-type substrate, by forming an N-type epitaxial layer on a surface, by forming an N-type well which involves a base region in an island of a low saturation N-P-N transistor alone to form the saturation NPN transistor, and by forming other element in a region except for the island. CONSTITUTION:An N-type buried layer 2 is formed in a P-type substrate 1, an N-type epitaxial layer 3 is formed on a surface, an N-type well 8 by diffusion of N-type impurities is formed only in an island of a low saturation NPN transis tor, and a structure is formed which involves a base region 5. Since it is equiva lent to change of an epitaxial concentration only in an island part of a transis tor which requires low saturation characteristics, an NPN transistor formed in the island has hFE which is several times as high as that of an NPN transis tor formed in other region. Furthermore, since a collector concentration increases, it functions to improve saturation characteristics in a low voltage region in a transistor whose base and emitter conditions are the same as those of conventional ones. Moreover, in other element, characteristics which depend on epitaxial conditions can be maintained.</p> |
