A semiconductor device comprising: a substrate; a drift region of a first conductivity type formed on a first main surface of the substrate and having a higher impurity concentration than the substrate; a well region of a second conductivity type extending in the drift region from a second main surface of the drift region in a direction perpendicular to the second main surface, the second main surface being opposite from a first main surface of the drift region in contact with the substrate; a source region of the first conductivity type extending in the well region from the second main surface in the perpendicular direction; a gate groove formed from the second main surface in the perpendicular direction and extending in contact with the source region, the well region in a direction parallel to the second main surface, and the drift region; a drain region of the first conductivity type formed away from the well region in the drift region and extending from the second main surface in the perpendicular direction; a gate insulating film formed on a surface of the gate groove; a gate electrode formed on a surface of the gate insulating film; a source electrode electrically connected to the source region and the well region; a drain electrode electrically connected to the drain region; a protection region of the second conductivity type formed in the drift region, on a surface of the gate insulating film facing the drain region; and a connection region of the second conductivity type formed in the drift region while being in contact with the well region and the protection region, wherein the well region and the protection region are electrically connected to each other by the connection region, and the protection region is in contact with an entire end surface of the gate groove facing the drain region. a substrate; a drift region of a first conductivity type formed on a first main surface of the substrate and having a higher impurity concentration than the substrate; a well region of a second conductivity type extending in the drift region from a second main surface of the drift region in a direction perpendicular to the second main surface, the second main surface being opposite from a first main surface of the drift region in contact with the substrate; a source region of the first conductivity type extending in the well region from the second main surface in the perpendicular direction; a gate groove formed from the second main surface in the perpendicular direction and extending in contact with the source region, the well region in a direction parallel to the second main surface, and the drift region; a drain region of the first conductivity type formed away from the well region in the drift region and extending from the second main surface in the perpendicular direction; a gate insulating film formed on a surface of the gate groove; a gate electrode formed on a surface of the gate insulating film; a source electrode electrically connected to the source region and the well region; a drain electrode electrically connected to the drain region; a protection region of the second conductivity type formed in the drift region, on a surface of the gate insulating film facing the drain region; and a connection region of the second conductivity type formed in the drift region while being in contact with the well region and the protection region, wherein the well region and the protection region are electrically connected to each other by the connection region, and the protection region is in contact with an entire end surface of the gate groove facing the drain region.