| 摘要 |
PROBLEM TO BE SOLVED: To suppress specific resistance of a semiconductor substrate, while improving an element breakdown voltage by setting a second conductivity-type region to a double layer of a heavily-doped layer at a surface side and a lightly- doped part that is deeper than the high-concentration layer and making specific the impurity concentration at the boundary of the two layers. SOLUTION: A second conductivity-type p-anode region 2, consisting of a P-anode region 21 with a low surface impurity concentration and a p+ anode region 22 with a high surface impurity concentration, is formed on one surface layer of an n-base layer 1 with a high specific resistance. A first conductivity- type n-cathode region 4 is formed on the other surface layer of the n-base layer 1. Then, by forming the p-anode region 2 with two layers, a depletion layer can be spread into the p--anode region 21 with a low impurity concentration when a voltage in inverse direction is applied, an electric field can be reduced, and the breakdown voltage of a semiconductor device can be improved. Especially, the impurity concentration at the boundary between the p+-anode region 22 and the p--anode region 21 are set to 5×1015 cm-3 or lower.
|
