| 摘要 |
PURPOSE:To augment the breakdown voltage as against the isolation withstanding voltage by a method wherein a low concentration region with curvature larger than that of the periphery of a buried region is provided laminating on the buried region. CONSTITUTION:A buried region 2 and a low concentration ion implanted layer i.e. a low concentration region 26 are formed as a laminated structure. The curvature of the junction on the substrate 1 side indicated by arrow marks is increased improving the breakdown voltage. In order to form such a structure, the mask of the buried region 2 may be used as it is and the diffusion of the ion implanted layer (low concentration region) may be performed together with the diffusion of the buried region 2 facilitating the operation. At this time, attention must be paid to the concentration of the ion implanted layer 26 as the low concentration region and the intrusion into a collector region because the concentration of said ion implanted layer 26 has to be considerably low considering the effect of intrusion into the collector region. |
