Patent ID: 6929728

Claim:
A sensor for measuring a gas concentration or ion concentration, said sensor comprising: a substrate of a first charge carrier type, a drain of a second charge carrier type formed on the substrate, a source of the second charge carrier type formed on the substrate, a channel area of the substrate located between the drain and the source, a conductive guard ring located outside the channel area, and a sensitive gate layer whose potential depends on the surrounding gas or ion concentration, with an air gap being provided between the gate layer and the channel area, wherein surface profiling is formed between the guard ring and the channel area, the surface profiling having elevations and depressions, the elevations being applied to a surface between an insulating thin layer in the channel area and the guard ring by deposition with the depressions formed between the elevations, the elevations being applied as insulating material to one or more insulating layers, and wherein the elevations are formed substantially concentrically with respect to the channel area.