A gas sensor comprising: - a dielectric substrate; - a first inert metal layer and a second inert metal layer which are formed on the dielectric substrate so that the inert metal layers (0202, 0206) have a prescribed distance from each other; - a first aluminum layer which covers a part of the surface of the first inert metal layer, the covered part of the surface of the first inert metal layer being deviated to the side of the second inert metal layer and which covers a part of a region of a surface of the dielectric substrate between the first and second inert metal layers (0202, 0206), the covered part of the region being deviated to the side of the first inert metal layer; - a semiconductor in the form of a film or layer, wherein the semiconductor is made of an organic material or a carbon nanomaterial, wherein the electric conductivity of the semiconductor varies in response to the degree of adsorption of gases, wherein the semiconductor covers a part of the surface of the first aluminum layer, the covered part of the surface of the first aluminum layer being deviated to the side of the second inert metal layer, and which covers a part of a region of the surface of the dielectric substrate between the aluminum layer and the second inert metal layer, the covered part of the region being deviated to the side of the first aluminum layer; and - a second aluminum layer which covers a part of the open top surface of the semiconductor, the covered part of the open top surface being deviated to the side of the second inert metal layer, and which covers a part of the surface of the second inert metal layer, the covered part of the surface of the second layer being deviated to the side of the first inert metal layer; wherein the first and second aluminum layers (203 and 205) have metallic parts (0203a, 0205a) respectively, and oxide parts (0203b, 0205b) which are formed at the interfaces facing the semiconductor. - a dielectric substrate; - a first inert metal layer and a second inert metal layer which are formed on the dielectric substrate so that the inert metal layers (0202, 0206) have a prescribed distance from each other; - a first aluminum layer which covers a part of the surface of the first inert metal layer, the covered part of the surface of the first inert metal layer being deviated to the side of the second inert metal layer and which covers a part of a region of a surface of the dielectric substrate between the first and second inert metal layers (0202, 0206), the covered part of the region being deviated to the side of the first inert metal layer; - a semiconductor in the form of a film or layer, wherein the semiconductor is made of an organic material or a carbon nanomaterial, wherein the electric conductivity of the semiconductor varies in response to the degree of adsorption of gases, wherein the semiconductor covers a part of the surface of the first aluminum layer, the covered part of the surface of the first aluminum layer being deviated to the side of the second inert metal layer, and which covers a part of a region of the surface of the dielectric substrate between the aluminum layer and the second inert metal layer, the covered part of the region being deviated to the side of the first aluminum layer; and - a second aluminum layer which covers a part of the open top surface of the semiconductor, the covered part of the open top surface being deviated to the side of the second inert metal layer, and which covers a part of the surface of the second inert metal layer, the covered part of the surface of the second layer being deviated to the side of the first inert metal layer; wherein the first and second aluminum layers (203 and 205) have metallic parts (0203a, 0205a) respectively, and oxide parts (0203b, 0205b) which are formed at the interfaces facing the semiconductor.