An apparatus for etching one side of a semiconductor layer, including at least one etching tank for receiving an electrolyte, a first electrode, which is arranged to make electrical contact with the electrolyte located in the etching tank during use, at least a second electrode, which is arranged to make indirect or direct electrical contact with the semiconductor layer, at least one electric current source, which is electrically conductively connected to the first and the second electrode to produce an etching current, and at least one transport apparatus for transporting the semiconductor layer relative to the etching tank in such a way that substantially only an etching side of the semiconductor layer that is to be etched can be wetted by the electrolyte located in the etching tank during use. The current source is formed as a variable current source, and that the apparatus has a controller for controlling the variable current source, wherein the apparatus is designed such that the etching current can be changed automatically by the controller during the etching operation. A method for etching one side of a semiconductor layer is also provided.