A method for controlling a thickness of a first layer of an electrical contact of a semiconductor device, whereby the semiconductor device comprises a semiconductor layer, a first layer and a second layer, whereby at least a part of the semi-conductor layer is covered with the first layer, whereby at least a part of the first layer is covered with the second layer, whereby the second layer is exposed to a plasma gas, whereby an upper face of the first layer adjacent to the second layer is treated by the plasma gas and an interlayer is generated between the first and the second layer reducing the thickness of the first layer.