SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME

In a vertical power MOSFET having a superjunction structure, the withstand voltage of the power MOSFET can be ensured even if the aspect ratios of an n-type column region and a p-type column region are increased so as to vary the impurity concentration of the p-type column region. P-type semiconductor regions PR1 are formed on the sides of an n-type column NC1 adjacent to a p-type column region PC1. In this configuration, the p-type semiconductor region PR1 is formed from the upper end of the n-type column region NC1 to about a half depth of a height from the upper end to the lower end of the side of the n-type column region NC1. This inclines the sides of the overall p-type column region including the p-type semiconductor regions PR1 and the p-type column region PC1.