A novel design of an interdigitated electrode array impedimetric sensor is proposed with electrode digits separated by an insulating barrier. This configuration results in that the major part of the electric current between electrodes follows close to the surface of the barrier and not through the solution thus permitting to enhance the sensitivity to possible chemical reactions on its surface. As a model system the effect of electrostatically assembled polyelectrolyte layers deposited using layer-by-layer method on the sensor impedance was studied. The sensitivity of the devices depends on the barrier height and is considerably enhanced comparing to conventional flat sensor structures. Devices may be used as a transducer for direct label-free biosensor development.