Method for manufacturing a sige channel field effect transistor

A method for manufacturing a field effect transistor comprising a silicon-germanium active layer and a gate oxide layer disposed on the active layer, the method comprising:

• providing a stack including a substrate, a silicon-germanium first layer disposed on the substrate and a silicon second layer disposed on the first layer;
• forming the gate oxide layer on the stack, and
• subjecting the stack to laser annealing so as to melt a region of the stack, said region comprising at least one part of the first layer and at least one part of the second layer, and recrystallising the molten region of the stack to obtain the silicon-germanium active layer in contact with the gate oxide layer, the active layer having a germanium concentration gradient;
• wherein the gate oxide layer is formed before the laser annealing or during the laser annealing.