A method of fabricating an electrode assembly of a sensor is described. The sensor has a field effect transistor. The electrode assembly is separated from the field effect transistor by only a conductive line. The sensor is functioned to detect different glucose concentrations. A solid layer of tin oxide is deposited on a substrate board. A β-D-glucose oxidase and polyvinyl alcohol bearing styrylpyridinium groups are placed in 100 μl of sulfuric acid, to form an enzyme mixture. The enzyme mixture is dropped on the solid layer of tin oxide. The enzyme mixture is dried. The enzyme mixture is exposed to a UV ray. The enzyme mixture is dried and stabilized. The enzyme mixture is immersed in a sulfuric buffer.