A semiconductor substrate (1) is provided with a source region (2) and a drain region (3) of a first type of electrical conductivity arranged at a surface (10) at a distance from one another, a channel region (4) of a second type of electrical conductivity, which is opposite to the first type of electrical conductivity, arranged between the source region (2) and the drain region (3), and a gate electrode (6) arranged above the channel region (4). A substrate well (7) of the first type of electrical conductivity is arranged in the substrate (1) at a distance from the source region (2). The substrate well (7) is contiguous with the drain region (3), and the distance between the source region (2) and the substrate well (7) is larger than the distance between the source region (2) and the drain region (3).