A method to selectively etch, and hence pattern, a semiconductor film deposited non-selectively is described. In one embodiment, a carbon-doped silicon film is deposited non-selectively such that the film forms an epitaxial region where deposited on a crystalline surface and an amorphous region where deposited on an amorphous surface. A four-component wet etch mixture is tuned to selectively etch the amorphous region while retaining the epitaxial region, wherein the four-component wet etch mixture comprises an oxidizing agent, an etchant, a buffer and a diluent.