Transistor device and method of processing contactor for semiconductor substrate

The invention relates to a transistor device and a method of processing a contactor for a semiconductor substrate. In an embodiment, a transistor device is provided, the transistor device comprising: a semiconductor substrate having a first main surface and a second main surface opposite the first main surface; a drain region of the first conductivity type formed on the second surface, a drift region of the first conductivity type formed on the drain region, a main body region of the second conductivity type formed on the drift region and opposite to the first conductivity type, and a source region of the first conductivity type formed on and/or in the main body region. A trench is disposed in the first surface, including a base and sidewalls. A gate electrode is arranged in the trench and is electrically insulated from the semiconductor substrate by a gate insulating layer, and a field plate is arranged in the trench below the gate electrode and is electrically insulated from the gate electrode and the semic