An implantable electrode device comprising a carrier made of a polymer material, wherein the carrier is flexible and electrically isolating, at least one measurement electrode formed by an electrically conducting pad located on the carrier, wherein the electrically conducting pad has a contact surface, at least one electrically conducting trace, and at least one electrically conducting terminal, wherein the trace electrically connects the measurement electrode and the terminal, wherein the implantable electrode device further comprises a barrier layer (8, 22) enclosing the carrier by covering all surfaces thereof, wherein the contact surface of the conducting pad is exposed to an outside environment, wherein the barrier layer (8, 22) is electrically isolating and impermeable for liquids, wherein the electrode device has a strip like shape, wherein the long sides of the electrode device having an essentially quadrangular footprint are straight lines, wherein the electrode device has a thickness in the range from 200 micrometers to 2,500 micrometres, wherein a thickness d below of a material below the electrically conducting material forming the measurement electrode, the electrically conducting trace and the electrically conducting terminal, and a thickness d above of a material above the electrically conducting material must fulfil the following simplified relation: Y below d below = Y above d above, wherein Y below is the Young's modulus of the material below the electrically conducting material and Y above is the Young's modulus of the material above the electrically conducting material and wherein a surface of the electrode device on a side on which the measurement electrode is located has a maximum valley depth or a maximum peak height between the contact surface of the measurement electrode and a meanline of the surface of the electrode device excluding the measurement electrodes being equal to or smaller than 60 micrometres or wherein a surface of the electrode device on a side on which the measurement electrode is located has a maximum valley depth or a maximum peak height between the contact surface of the measurement electrode and a meanline of the surface of the electrode device excluding the measurement electrodes being larger than 60 micrometres and wherein the maximum linear extension of the contact surface is equal to or less than 100 micrometres. a carrier made of a polymer material, wherein the carrier is flexible and electrically isolating, at least one measurement electrode formed by an electrically conducting pad located on the carrier, wherein the electrically conducting pad has a contact surface, at least one electrically conducting trace, and at least one electrically conducting terminal, wherein the trace electrically connects the measurement electrode and the terminal, wherein wherein the electrically conducting pad has a contact surface, at least one electrically conducting trace, and at least one electrically conducting terminal, wherein the trace electrically connects the measurement electrode and the terminal, wherein the implantable electrode device further comprises a barrier layer (8, 22) enclosing the carrier by covering all surfaces thereof, wherein the contact surface of the conducting pad is exposed to an outside environment, wherein the barrier layer (8, 22) is electrically isolating and impermeable for liquids, wherein the electrode device has a strip like shape, wherein the long sides of the electrode device having an essentially quadrangular footprint are straight lines, wherein the electrode device has a thickness in the range from 200 micrometers to 2,500 micrometres, wherein a thickness d below of a material below the electrically conducting material forming the measurement electrode, the electrically conducting trace and the electrically conducting terminal, and a thickness d above of a material above the electrically conducting material must fulfil the following simplified relation: Y below d below = Y above d above, wherein Y below is the Young's modulus of the material below the electrically conducting material and Y above is the Young's modulus of the material above the electrically conducting material and wherein a surface of the electrode device on a side on which the measurement electrode is located has a maximum valley depth or a maximum peak height between the contact surface of the measurement electrode and a meanline of the surface of the electrode device excluding the measurement electrodes being equal to or smaller than 60 micrometres or wherein a surface of the electrode device on a side on which the measurement electrode is located has a maximum valley depth or a maximum peak height between the contact surface of the measurement electrode and a meanline of the surface of the electrode device excluding the measurement electrodes being larger than 60 micrometres and wherein the maximum linear extension of the contact surface is equal to or less than 100 micrometres.