Semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate having a first main surface and a second main surface;
• and
• a first polysilicon layer and a second polysilicon layer doped with an impurity,
• wherein the semiconductor substrate includes a diffusion layer doped with an impurity,
• wherein the diffusion layer is located between the first main surface and the second main surface,
• wherein a first groove and a second groove are formed on the first main surface in a spaced-apart relationship along a first direction in a plan view,
• wherein each of the first groove and the second groove extends along a second direction orthogonal to the first direction in a plan view and extends toward the second main surface so as to reach the diffusion layer in a cross-sectional view orthogonal to the second direction,
• wherein the first polysilicon layer and the second polysilicon layer are embedded in the first groove and the second groove, respectively, and
• wherein a lower end of the first polysilicon layer and a lower end of the second polysilicon layer are electrically connected to each other by the diffusion layer.