A flat display device preferably of the PALC type in which a fragile micro-sheet covering the plasma channels is replaced by a more robust plate having etched spaced elongated cavities configured in such a way that the top portions of the plate between side walls of each cavity defining a channel and facing the bottom plate are substantially flat. Preferably, the thickness of the glass top plate separating each plasma discharge from an electro-optic pixel is made substantially uniformly thin while the side walls reinforce and greatly increase the strength of the plate making it less prone to breakage during assembly of a display panel. Preferably, the glass plate is etched by means of a plasma etching process.