Abstract: In order to obtain long time stability and usefulness for gas sensitive field-effect devices a micro structured surface is obtained below the final conducting layer. The conductive layer in the trenches or grooves will not only be protected to some extent but also they can constitute a conductive net with edges or boundaries that will remain essentially unchanged even if material is continuously lost along the borderline. The structure can be obtained in the layer laying directly below the conductive layer or in deeper lying layers with intermediate layers with even thickness.

Abstract: Electronic odor detecting device (electronic nose) provided with a number of sensors. The gas that is to be subjected to the detection is brought to pass a number of similar or different sensors distributed on a surface. Between the sensors or actually extending between and past the sensors is a catalyst. The catalyst may be arranged on an opposing wall in a detection cell or in the same surface as the sensors. Constituents of the gas that react with the catalyst result in a different signal pattern for the sensors, depending on their location in relation to the catalyst. Since different substances in the gas will react with different rates in the presence of the catalyst, the sensed pattern will change along the catalytic surface. This makes it possible to evaluate a gas mixture with great precision and with a more limited number of sensors in comparison to prior art.