Abstract: An electrode structure includes a conductive film 24c formed on a base substrate 10 through an insulation film. The insulation film comprises a plurality of poles 36 of polyimide, a first film 38 formed on the side surfaces of the poles and formed of an insulation material of a high hardness than polyimide, and a second film 40 of polyimide buried among the plural poles with the first film formed on the side surfaces thereof. Because of the first film of an insulation material having high hardness formed on the side surfaces of the poles of polyimide, even when a strong force is applied upon the bonding, the poles are prevented from being distorted, and the conductive film is protected from peeling off. Because of the thick polyimide layer below the conductive film, a parasitic capacity between the conductive film and the lower layer can be small, whereby radio-frequency signals can be used.