For example, contact grooves or contact trenches 245 are formed in the cell mesa region 220 between the gate trenches 240 and the field plate trenches 230. The contact trenches 245 extend from the first side 201 through source regions 251 and into body regions 252 as shown in FIG. 2A. The contact trenches 245 are less deep than the gate trenches 240 which extend from the first side 201 through the source region 251 and the body region 252 and into the drift region 253 arranged below the body region 252 and between adjacent field plate trenches 230.
As shown in FIG. 2A, the field plate trench 230 extends much deeper into the semiconductor substrate 200 than the gate trench 240. Adjacent field plate trenches 230 thus define and border a cell mesa region 220 which includes at the first side 201 of the semiconductor substrate 200 the source region 251, the body region 252 and a large part of the drift region 253. The field electrodes 231 are typically electrically connected to the source regions 251 and are therefore at source potential. When the semiconductor device is operated in blocking mode, the field electrodes 231 being on source potential contribute to the depletion of the drift region 253 between adjacent field trenches 230. This improves the blocking capabilities of the device and allows to provide the drift region with a higher doping concentration to reduce the on-state resistance RON.
