Multilayer passivation of the upper face of the stack of semiconductor materials of a field-effect transistor

A field-effect transistor comprising:

• a stack of semiconductor materials along the axis z comprising a binary or ternary or quaternary nitride compound;
• a drain, a source and a gate;
• a passivation layer 464 disposed on top of the upper face of said stack, said passivation layer comprising two sub-layers;
• wherein said drain, said source and said gate define:
• a first zone of high electric field intensity at the base of the gate between the gate and the drain or between the gate and the source when an electric voltage difference is applied between the drain and the source or between the gate and the source, and
• a second zone of low electric field intensity;
• and wherein:
• said first sub-layer extends over the second zone, comprises a first material with an electric breakdown field Ecl1, the electrical charge of said first sub-layer being strictly less than the electrical charge of said upper face of the stack,
• said second sub-layer extends over the first zone, covers the first sub-layer and comprises a second material with an electric breakdown field Ecl2 strictly greater than Ecl1.