| 摘要 |
PURPOSE:To optimize the dielectric strength and other characteristics of each of the elements formed on the same substrate, by forming separating layers which surround one element as well as have a depth larger than at least that of a layers, at an interval. CONSTITUTION:On an N type silicon substrate 1, an N type epitaxial layer 2 is formed, and a P type lower surface-separating layer 3 to separate a small signal transistor (Tr), and a floating collector 4 are formed therein. Moreover, a low- concentration N type epitaxial layer 5 is formed thereon. When a base 6 of a power transistor and separating layers 7 and 8 of the small signal transistor are to be formed, simultaneously, guard ring layers 17 and 18 are formed so as to surround the periphery of the base 6 as well as reach at least the layer 2, at an interval. Owing to said separating layers 17 and 18, the field strength at this partion becomes weaker than that beneath the base, so that breakdown takes place mainly beneath the bases 6 and 12. |
