Method of making an integrated circuit, the method comprising: - providing a semiconductor substrate; - forming an electrical impedance based gas sensor on a passivation layer of the substrate, the sensor comprising first and second electrically conductive sensor electrodes, wherein each sensor electrode is enclosed in an electrically conductive corrosion protection material; and - depositing a gas sensitive material located between the sensor electrodes, the gas sensitive material having an impedance that is sensitive to gas to be sensed, wherein forming the first and second electrically conductive sensor electrodes enclosed in an electrically conductive corrosion protection material comprises: - depositing a first layer of the electrically conductive corrosion protection material; - depositing an electrically conductive electrode layer on the first layer of the electrically conductive corrosion protection material; - depositing a second layer of the electrically conductive corrosion protection material on the electrically conductive electrode layer, - patterning the deposited layers to form the sensor electrodes, each electrode comprising a stack of a first layer of the electrically conductive corrosion protection material, the electrically conductive electrode layer and a second layer of the electrically conductive corrosion protection material; - covering the stacks with a layer of the corrosion protection material, and - using a directional etch to remove the portions of the material that lie in intervening portions on the substrate such that the directional etch etches in a direction downwards towards the substrate, whereby material on top of the stacks and material in-between the stacks tends to be etched away, while portions of the corrosion protection material on the side walls of the stacks are retained. - providing a semiconductor substrate; - forming an electrical impedance based gas sensor on a passivation layer of the substrate, the sensor comprising first and second electrically conductive sensor electrodes, wherein each sensor electrode is enclosed in an electrically conductive corrosion protection material; and - depositing a gas sensitive material located between the sensor electrodes, the gas sensitive material having an impedance that is sensitive to gas to be sensed, - depositing a first layer of the electrically conductive corrosion protection material; - depositing an electrically conductive electrode layer on the first layer of the electrically conductive corrosion protection material; - depositing a second layer of the electrically conductive corrosion protection material on the electrically conductive electrode layer, - patterning the deposited layers to form the sensor electrodes, each electrode comprising a stack of a first layer of the electrically conductive corrosion protection material, the electrically conductive electrode layer and a second layer of the electrically conductive corrosion protection material; - covering the stacks with a layer of the corrosion protection material, and - using a directional etch to remove the portions of the material that lie in intervening portions on the substrate such that the directional etch etches in a direction downwards towards the substrate, whereby material on top of the stacks and material in-between the stacks tends to be etched away, while portions of the corrosion protection material on the side walls of the stacks are retained.