SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD OF THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a sheeted semiconductor device which satisfies both of high breakdown voltage and reduction in snappy behavior.SOLUTION: A semiconductor device comprises: a first conductivity type semiconductor substrate having a surface and a rear face; a first conductivity type first impurity layer provided on the rear face side of the semiconductor substrate; and a first conductivity type second impurity layer provided closer to the rear face than the first impurity layer. A majority carrier concentration in the first impurity layer in a thermal equilibrium state has a downward projecting concentration which monotonously decreases in a plate thickness direction from the rear face toward the surface of the semiconductor substrate, and the maximum value of the majority carrier concentration is smaller than the maximum value in the second impurity layer and larger than the maximum value in the semiconductor substrate. A thickness of the first impurity layer in the plate thickness direction is equal to or larger than 0.15 times larger than a thickness of the semiconductor substrate. The maximum value of the majority carrier concentration in the second impurity layer in a thermal equilibrium state is equal to or larger than two times larger than the maximum value in the first impurity layer. A thickness of the second impurity layer in the plate thickness direction is equal to or smaller than 0.1 times larger than a thickness of the first impurity layer in the plate thickness direction.