| 摘要 |
PURPOSE:To prevent the lowering of withstanding voltage between a base and a collector at low currents by surrounding other residual base regions through a high-resistance isolation layer by one base region of a plurality of base regions while forming a guard ring layer on the outside of one base region through the high-resistance isolation layer. CONSTITUTION:An N-type impurity is diffused selectively to an N-type substrate to shape a collector layer 1, a base region 2 in a pre-step transistor A is surrounded insularly by a base region 3 in a post-step transistor B through a high-resistance isolation layer 10, and a P-type impurity is diffused selectively so as to form guard ring layers 4, 5, 6 around these regions. An N-type impurity is diffused selectively to the base regions 2, 3 and the outside of the guard ring layer 6, thus forming emitter regions 7, 8 and a channel stopper region 9. Accordingly, when bias voltage is applied between the base 2 and a collector 1 in the pre-step transistor A, there is no concentration section of an electric field, and withstanding voltage between the base and the collector is kept constant regardless of the magnitude of currents. |
