SEMICONDUCTOR DEVICE

PURPOSE:To obtain an element of a stable breakdown voltage without the instability at an end part by improving the region at a part crossed with the surface of a semiconductor substrate at the end part of a P-N junction. CONSTITUTION:The P-N junction 3 is constructed by forming a conductive region 1 of different conductivity type (N type) in the first conductive region (e.g. P type) 2 of the semiconductor substrate. An insulation film 5 and an electrode 6 are formed on the surface of the substrate. The third conductive region 10 is provided by introducing an impurity to the end parts 4 of the P-N junction of the region 1. This third conductive region 10 is e.g. N type; the depth from the surface of the substrate is made equal to that of the conductive region 1 or shallower than it, and the impurity concentration is formed lower than that of the region 1 and higher than that of the region 2. Or, the conductive region 10 is changed e.g. P type, and the inpurity concentration is made lower than that of the region 2. In other words, the impurity concentration of the region 2 is cancelled to a degree that the conductivity inversion does not occur.