Miniaturized planar back-side contact transducers (BSC) with chemically modified gold surface have been utilized as electrochemical sensors. The electrodes have been functionalized by sequential immobilization of aryl diazonium salts or alkanethiols and short peptide Gly-Gly-His. The applicability of gold substrates modified with aryl diazonium salts in voltammetric detection of copper(II) ions in aqueous solutions has been studied. The combination of two fundamental elements of the solid-state electrode, i.e. back-side contact (BSC) gold sensor and self-assembled monolayers, allowed one to obtain reliable miniaturized copper(II) ion sensors. It can have important future applications in environmental sensing or in implantable biodevices.