| 摘要 |
PURPOSE:To reduce junction capacity and improve the high-frequency characteristic of the transistor by reducing the density gradient of impurity in the junction of a semiconductor substrate and a floating collector layer containing impurity of high density. CONSTITUTION:An n type layer 9 containing impurity of low density is diffused deep beforehand in a p type Si substrate 1 by injection of ion or the like. Nixt, the n<+> type floating collector layer 2 containing impurity of high density is formed through diffusion. In the boundary part between the n<+> type floating collector layer 2 and the p type Si substrate 1 the n type layer 9 exists, thereby the density gradient of impurity from the n<+> type floating collector layer to the p type Si layer is reduced, and the junction capacity Csc is also reduced. Thus, a time constant determined by the junction capacity and the resistance of the substrate is reduced and the high-frequency charactersitic of the transistor can be improved. |
