| 摘要 |
A protective diode (101) has a basic structure (103) including an n + layer (11), an n- layer (10), a p + layer (12), and an n - layer (10) in this order. A p-type layer forming the protective diode (101) is the p + layer (12) with high impurity concentration. Therefore, the spreading of a depletion layer is suppressed and it is possible to reduce the area of the protective diode (101). In addition, phosphorus ions with a large diffusion coefficient are implanted to form the n - layer (10) with low impurity concentration in the polysilicon layer (9) forming the protective diode (101). A heat treatment is performed at a temperature of 1000°C or higher to diffuse the phosphorus ions implanted into the polysilicon layer (9). Therefore, the impurity profile of the n - layer (10) in the depth direction can be uniformized in the depth direction. As a result, a pn junction surface between the p + layer (12) with high impurity concentration and the n - layer (10) with low impurity concentration is substantially perpendicular to the main surface of the substrate and it is possible to suppress the concentration of the electric field on the pn junction between the p + layer (12) and the n - layer (10). |
