Field-effect controlled transistors, such as MOSFETs (Metal Oxide Field-Effect Transistors) are widely used in automotive, industrial, or consumer electronic applications for driving loads, converting power, or the like. Such transistors, which are often referred to as power transistors, are available with different voltage blocking capabilities. The “voltage blocking capability” defines the maximum voltage level the transistor can withstand in an off-state (when switched off). The on-resistance RON of a power transistor is another relevant device parameter. The “on-resistance” is the electrical resistance of the power transistor between its load nodes (drain node and source node) in the on-state (when switched on). Typically, a power transistor includes a plurality of transistor cells that are connected in parallel. Basically, the more transistor cells the power transistor includes the lower is the on-resistance.
There is a need to reduce the on-resistance without increasing the size (the required chip area A) of the semiconductor body (semiconductor chip) in which active areas of the power transistor are integrated. There is therefore a need to reduce the size of the individual transistor cells.