Conductor etching for producing thin-film transistor devices

A method for producing thin-film transistor devices comprises forming an organic polymer insulator 8 over a first conductor pattern 4 defining a first level of conductors, forming a protection layer 10 over the organic polymer insulator and forming a conductive layer 12 over the protection layer. The conductive layer 12 is patterned by a liquid etchant to define a second level of conductors. The protection layer and the organic polymer insulator comprise materials that exhibit a substantially zero etch rate for the liquid etchant. The protection layer is less permeable to the liquid etchant and/or is more resistant to damage by the liquid etchant than the organic polymer insulator, protecting the first conductor pattern from damage. The protection layer may be a first conductive layer, for example an inorganic oxide material such as Indium Tin Oxide (ITO), or an insulating layer such as silicon nitrides, silicon oxides, aluminium nitrides, aluminium oxides, indium gallium zinc oxide (IGZO), indium gallium oxide (IGO) and titanium oxides (TiOx).