A semiconductor device includes a source zone electrically connected to a first load terminal, a contiguous zone isolating the source zone from a drift zone, and a trench extending into a semiconductor body along a vertical direction and including a first electrode electrically connected to a control terminal and an insulator in contact with the contiguous zone and which isolates the first electrode from the semiconductor body. The insulator has, at a trench bottom region, a first thickness along the vertical direction, and, at a trench top region, a second thickness along a lateral direction, the first thickness being greater than the second thickness by a factor of at least 1.5. The contiguous zone is arranged in contact with the insulator and extends further along the vertical direction than the trench, and the trench bottom region and the contiguous zone overlap along the lateral direction.