Semiconductor device

A semiconductor device, comprising:

• a first electrode layer;
• a second electrode layer apart from the first electrode layer in a thickness direction;
• and
• a semiconductor substrate including a first principal surface in contact with the first electrode layer, and a second principal surface in contact with the second electrode layer and opposite to the first principal surface in the thickness direction, the semiconductor substrate including:
• a drift layer of n-type;
• and
• a first buffer layer of n-type between the first principal surface and the drift layer, the first buffer layer including:
• a first region containing protons, being higher in impurity concentration than the drift layer, and being in contact with the drift layer;
• a second region containing protons, being higher in impurity concentration than the drift layer, being disposed between the first region and the first principal surface, and being in contact with the first region;
• and
• a third region between the second region of the first buffer layer and the first principal surface of the semiconductor substrate,
• wherein the first buffer layer has an impurity concentration profile depending on a depth distance from the first principal surface along the thickness direction, and
• the impurity concentration profile includes:
• a maximum value in the second region as a maximum value of the impurity concentration profile of the first buffer layer;
• a kink at a boundary point between the first region and the second region, the kink relaxing or stopping a decrease from the maximum value;
• a value at the boundary point, the value being higher than or equal to 80% of the maximum value;
• and
• a distribution of the third region, the distribution being longer than or equal to 5 μm and having an impurity concentration lower than the value at the boundary point and lower than or equal to 5.0×1014/cm3.