| 摘要 |
PURPOSE:To increase an inverse withstand voltage against a separate voltage by a method wherein around a circumference of an embedded layer, an inverse conduction type protective ring having a radius of curvature larger than the outer circumference of the embedded layer. CONSTITUTION:An N<+> embedded collector 7 is installed on a p type substrate 1 and along the outer circumference, an N<+> protective annular layer is laid thereupon. When an impurity having a diffusion coefficient larger than the layer 7, the radius of curvature of the outer peripheral face of the layer 8 is larger than the layer 7. Next thereto, an N epitaxial layer is installed, as if surrounding layers 7, 8, an area is separated by P layers 3a, 3b. Within an island area 2a, a bipolar transistor element is formed. With this constitution, a part having a small radius of curvature of the embedded layer 7 is coated with the protective ring 8 having a large radius of curvature, as a result, an inverse withstand voltage is increased. |
