A sensor is configured to measure the carbon dioxide concentration in a gas mixture. The sensor has a dielectric layer arranged between a layer-like first electrode and a layer-like second electrode. The second electrode is a composite electrode that has at least one carbonate and/or one phosphate as first material and at least one metal as second material. This sensor can be manufactured by a method comprising applying a layer-like first electrode to a substrate, applying a dielectric layer to the first electrode, and applying a layer-like second electrode to the dielectric layer. The second electrode is applied as a composite electrode that has at least one carbonate and/or one phosphate as first material and has at least one second material that has an electrical conductivity of more than 10-2 S/m.