GAS SENSOR WITH BRIDGE STRUCTURE

A gas sensor comprises a silicon substrate (1) having a recess or opening (2) formed therein. A thin-film bridge (3) is arranged over the recess or opening and forms a hotplate (6) receiving a patch (8) of sensing material. The hotplate (6) is formed by a circular central section (5) of the bridge (3), which is connected to the substrate (1) by means of two thin arms. A first metal layer (12) of tungsten or platinum or gold and a second metal layer (14) of platinum or gold are arranged in the bridge (3), separated by a dielectric layer (13). The first metal layer (12) forms a heater (20), while the second metal layer (14) forms at least part of the electrodes (30, 31) for contacting the sensing material. A temperature sensor (34) can be formed by the first and/or by the second metal layer (14). Openings extending through the bridge (3) can be used to prevent delamination.