| 摘要 |
PURPOSE:To suppress the auto-doping quantity while placing epitaxial layers and to obtain a semiconductor device having high pressure resistance and small junction capacity and high switching speed, by a method wherein the first and the second buried areas with different inpurities density are formed. CONSTITUTION:The first and the second N<+> type buried areas with different impurity densty are formed on a P type semiconductor base plate 1. Insulating materials 4, which separate island area 3' by placing N<-> type epitaxial layer, are formed, and its surface is covered with an insulating film 5, and windows are opened and diffused, and N<+> type collector lead out areas 8, P<+> type base areas 7, N<+> type emitter areas 8 and electrodes 9 are formed. Surface density of the first buried area 2 before epitaxial layer is formed, is made under 50-80% of buried area 2' of the second normal density, and impurity quantity by the auto- doping, which is taken into during the deposition of epitaxial layer, is reduced. |
