A semiconductor device includes a transistor in a semiconductor substrate having a first main surface. The transistor includes a source region, a drain region, a channel region, a drift zone, and a gate electrode adjacent to at least two sides of the channel region. The channel region and the drift zone are disposed along a first direction parallel to the first main surface, between the source region and the drain region. The semiconductor device further includes a conductive layer beneath the gate electrode and insulated from the gate electrode.