| 摘要 |
PURPOSE:To improve the frequency characteristics and to reduce a collector saturation resistance of a semiconductor device by equalizing or enhancing the impurity concentration of a bipolar transistor forming region to or higher than that of a P-channel MOS transistor forming region. CONSTITUTION:An N<+> type buried layer 3 and P<+> type buried layers 4, 4A are formed on a P-type semiconductor substrate 1, an N<+> type epitaxial layer 2A is formed thereon, and a P<+> type wall layer 5 and a P<+> type layer 6 for dielectric isolation are formed in the layer 2A. An N-channel MOS transistor is formed on the layer 5, and P-channel MOS transistor and a bipolar transistor are formed in the P-channel MOS transistor and the bipolar transistor forming regions in the layer 2A. Thus, since the bipolar transistor is formed in the N<+> type epitaxial layer having the same high impurity concentration as that of the P-channel MOS transistor forming region, frequency characteristics are improved, and a collector saturation resistance is reduced. |
