and is provided for example as an algan layer having suitably high doping for example n doping other layer sequences may also be used in the stack 2 if other electronic properties are required the basic construction remains the same in terms of the position and orientation relative to the regions 24 a 24 b in the manufacturing phase shown the stack 2 is modified in such a way that an hemt is fabricated therefrom a source region s of the hemt is positioned vertically above the insulated region 24 a and a drain region d is positioned vertically above the region 24 b the horizontal length of the hemt is determined inter alia by the required breakdown voltage i e by the length of the depletion region between the source s and the drain d as explained above the vertical height of the iii v semiconductor layer 30 can be made very thin since the iii v semiconductor 30 does not have to receive the entire drain voltage in the vertical direction but the active layer 24 i e in particular the region 24 b and to some extent also the region 24 a can take over part of the voltage stability further the stack 2 comprises an electrode g which u2014 based on adapted structuring u2014 acts as a gate electrode for the hemt the electrode thus has an adapted shape for the transistor operation in such a way that in particular a desired gate length is defined the electrode g can be applied directly to the layer 62 or a thin insulator layer not shown may be provided between the electrode g and the layer 62 so as to reduce the gate leakage currents the gate.