Sandwich sensor for the determination of an analyte concentration

implantable sensor (110) for determining the concentration of at least one analyte in a medium, particularly in a body tissue and / or in a body fluid, wherein the implantable sensor (110) has a structure layers with at least a substrate insulating support (112; 210, 216; 710, 712, 714; 810, 812) and at least two electrodes (134, 136; 238, 240, 242; 738, 740, 742, 830, 832, 836) arranged in at least two planes of different coating implantable sensor (110) and electrically separated from each other by the substrate or substrates insulative support (112; 210, 216; 710, 712 , 714; 810, 812) with electrode surfaces that are directed toward the middle when the sensor (110) is implanted and in contact with the medium, either directly or through a membrane layer (146) permeable to the analyte, and essentially large surfaces evenly, wherein the implantable sensor (110) further contact layers (114, 116; 212, 214; 222; 610, 612; 716, 718, 720; 814, 816, 822) that establish contact with at least two electrodes (134, 136; 238, 240, 242; 738, 740, 742; 830, 832, 836), characterized in that the substrate or substrates insulative support (112; 210, 216; 710, 712, 714; 810, 812) have a width, two electrodes (134, 136 extending the least; 238, 240, 242; 738, 740, 742; 830, 832, 836) and / or at least two contact layers (114, 116; 212, 214; 222; 610, 612; 716, 718, 720; 814, 816, 822) along the entire width substrate or substrates insulative support (112; 210, 216; 710, 712, 714; 810, 812).