An implantable electrode device includes a carrier made of a polymer material, at least one measurement electrode formed by an electrically conducting pad located on the carrier, wherein the electrically conducting pad has a contact surface, a barrier layer enclosing the carrier by covering all surfaces of the carrier, wherein the contact surface of the electrically conducting pad is exposed to an outside environment, at least one electrically conducting trace, and at least one electrically conducting terminal. The electrically conducting trace can electrically connect the measurement electrode to the electrically conducting terminal. A surface of the implantable electrode device on a side on which the measurement electrode is located can have a maximum valley depth or a maximum peak height between the contact surface of the measurement electrode and a meanline of a surface of the implantable electrode device, excluding measurement electrodes, being equal to or smaller than 100 micrometres.
