| 摘要 |
A semiconductor layer has a second impurity concentration. First trenches are formed in the semiconductor layer to extend downward from an upper surface of the semiconductor layer. Each of insulation layers is formed along each of the inner walls of the first trenches. Each of conductive layers is formed to bury each of the first trenches via each of the insulation layers, and extends downward from the upper surface of the semiconductor layer to a first position. A first semiconductor diffusion layer reaches a second position from the upper surface of the semiconductor layer, is positioned between the first trenches, and has a third impurity concentration lower than the second impurity concentration. A length from the upper surface of the semiconductor layer to the second position is equal to or less than half a length from the upper surface of the semiconductor layer to the first position.
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