A semiconductor device is provided, which includes a substrate; a P-N column layer disposed on the substrate; a second conductivity type epitaxial layer disposed on the P-N column layer. The P-N column layer includes first conductivity type columns and second conductivity type columns, which are alternately arranged. Each column has a tapered shape. A portion of the first conductivity type column located around the substrate has a smaller impurity concentration than another portion of the first conductivity type column located around the second conductivity type epitaxial layer. A portion of the second conductivity type column located around the substrate has a larger impurity concentration than another portion of the first conductivity type column located around the second conductivity type epitaxial layer.