SEMICONDUCTOR DEVICE HAVING A RETROGRADE WELL STRUCTURE AND METHOD OF MANUFACTURING THEREOF

摘要

A semiconductor substrate is of a first conductivity type and has a first impurity concentration. A first impurity layer of the first conductivity type and having a second impurity concentration with an impurity concentration peak is formed on a main surface of the semiconductor substrate. A second impurity layer of a third impurity concentration comes into contact with the underside of the first impurity layer. The third impurity concentration is smaller than the impurity concentration peak of the first impurity concentration and the second impurity concentration. An element is formed on the first impurity layer.