A semiconductor device includes a first transistor cell including a first gate electrode in a first trench. The semiconductor device further includes a second transistor cell including a second gate electrode in a second trench, wherein the first and second gate electrodes are electrically connected. The semiconductor device further includes a third trench between the first and second trenches, wherein the third trench extends deeper into a semiconductor body from a first side of the semiconductor body than the first and second trenches. The semiconductor device further includes a dielectric in the third trench covering a bottom side and walls of the third trench.