| 摘要 |
PURPOSE:To improve latch-up resistance by forming a buried layer of concentration higher than a substrate just under sections except an island while forming a buried layer of concentration higher than the island just under the island. CONSTITUTION:The n<+> type buried layer 112 is formed just under sections except the p<-> type island 106 while the p<+> type buried layer is formed just under the island 106. When positive surge voltage is applied to an output terminal OUT, the base concentration of pnp transistors TRs 1, 2 becomes higher when the layer 112 is formed so as not to be in contact with the island 106. Accordingly, numbers of which carriers recombine in a base increase, flowing currents reduce only by the increase, an amplification factor drops, and latch-up resistance increases. An n<+> of high concentration of the layer 112 does not collide with the island 106 even when it floats. The amplification factor of a parasitic n-p-n TR does not increase because the base length of npn TRs 3, 4 also does not change. Since the layer 113 is formed, the base concentration of the parasitic npn TR increases, and the amplification factor can be lowered. |
