| 摘要 |
PURPOSE:To enhance the withstand voltage of P-N junction by a method wherein diffusion of impurity gas is repeated to the surface of a wafer to form a conductive region having a large radius of curvature in the direction of the deep part of the bottom corner part. CONSTITUTION:The surface of the N type conductive region 1 of the wafer is masked with an oxide film 5 of silicon oxide having a window 4, impurity gas is diffused through the window 4 to form the deep P type conductive region 2 in a narrow range. The surface is masked with the oxide film 5 extending the window 4 a little to form the P type conductive region 2 a little shallower than the last time, the process thereof is repeated in order to form the P type conductive region 2 having the large radius of curvature in the direction of the deep part of the bottom corner part 3. The radius of curvature of a depletion layer 6 at the corner part 3 is enlarged as compared with the case when the conductive region having the same depth is formed by one time diffusion, and the withstand voltage of P-N junction can be enhanced sharply. |
