SEMICONDUCTOR DEVICE

To provide a semiconductor device capable of suppressing a reduction in breakdown voltage and reducing a resistance of an epitaxial layer.SOLUTION: Provided is a semiconductor device 1 including: an n type semiconductor substrate 2 including an n type impurity having a diffusion coefficient less than a diffusion coefficient of phosphorus; an n type epitaxial layer 6 including a high concentration region 11, an intermediate concentration region 12, and a low concentration region 13 formed on the semiconductor substrate 2 in this order, and having an n type impurity concentration gradient formed in a downward step-wise manner from the semiconductor substrate 2 toward a crystal growth direction by the high concentration region 11, the intermediate concentration region 12, and the low concentration region 13; and a trench structure 21 including a trench 22 formed in the low concentration region 13, an insulation layer 23 formed on an inner wall of the trench 22, and an embedded electrode 24 embedded in the trench 22 with the insulation layer 23 interposed therebetween.SELECTED DRAWING: Figure 2 【課題】ブレークダウン電圧の低下の抑制、および、エピタキシャル層の低抵抗化を図ることができる半導体装置を提供する。【解決手段】燐の拡散係数未満の拡散係数を有するｎ型不純物を含むｎ型の半導体基板２と、半導体基板２の上にこの順に形成された高濃度領域１１、中濃度領域１２および低濃度領域１３を含み、高濃度領域１１、中濃度領域１２および低濃度領域１３によって半導体基板２から結晶成長方向に向けて下り階段状に形成されたｎ型不純物濃度勾配を有するｎ型のエピタキシャル層６と、低濃度領域１３に形成されたトレンチ２２、トレンチ２２の内壁に形成された絶縁層２３、および、絶縁層２３を挟んでトレンチ２２に埋設された埋設電極２４を含むトレンチ構造２１と、を含む、半導体装置１を提供する。【選択図】図２