A flexible circuit electrode array device comprising: a polymer layer; wherein the polymer layer includes one or more metal traces, an electrode array; one or more bond pads; and the electrode array is located on the opposite side of the polymer layer. A method for backside processing of a flexible circuit electrode device, comprising: applying polymer film on a substrate; processing the front side; releasing the polymer film from substrate; flipping over the polymer film and fixing it onto the substrate; processing the backside; and final releasing of the polymer film from the substrate. Another aspect of the method involves backside processing of a flexible circuit electrode device, comprising: processing the front side without releasing the polymer; processing the backside by sacrificial substrate method, or by laser drilling method; and releasing the polymer film from the substrate.