Semiconductor device and method for manufacturing the same

A semiconductor device comprising:

• a first electrode;
• a first semiconductor layer of a first conductivity type provided on the first electrode;
• a first pillar of a second conductivity type provided on the first semiconductor layer, the first pillar having a first average concentration of impurities of the second conductivity type;
• a second pillar of the first conductivity type provided on the first semiconductor layer, and including a first layer having a second average concentration of impurities of the first conductivity type, that is lower than the first average concentration, and a second layer having a third average concentration of impurities of the first conductivity type, that is higher than the first average concentration;
• a second semiconductor layer of the second conductivity type provided on the second pillar;
• a third semiconductor layer of the first conductivity type provided on the second semiconductor layer;
• a second electrode connected to the first pillar and the third semiconductor layer;
• a third electrode;
• and
• an insulating film disposed between the second semiconductor layer and the third electrode, wherein
• a difference between a maximum value and a minimum value of the impurity concentrations in the first layer is smaller than a difference between a maximum value and a minimum value of the impurity concentrations in the second layer, and
• a difference between a maximum value and a minimum value of the impurity concentrations in the first pillar is greater than the difference between the maximum value and the minimum value of the impurity concentrations in the first layer, and smaller than the difference between the maximum value and the minimum value of the impurity concentrations in the second layer.