A functional molecule (10) is constructed of electrodes (5,6), which are formed of pSi (polysilicon) and are opposing each other, and a molecular array structure (7), and the molecular array structure is formed of interface modifier molecules (2), which are covalently coupled to surfaces of the electrodes (5,6) to modify the surfaces, and driver molecules (1) repeatedly stacked in one direction between the interface modifier molecules. The interface modifier molecules each have a nearly discoid skeleton of a π-electron conjugated system and side chains, are arranged with planes of their skeletons lying substantially in parallel to the surfaces of both the electrodes, and are covalently coupled at their side chains to Si atoms in both the electrodes. The driver molecules are of a π-electron conjugated system, and upon application of an electrical field, change in structure or orientation and hence change in dielectric constant, in other words, conductivity. The driver molecules are functional molecules of a complex having a Zn ion approximately at its center. The interface modifier molecules and driver molecules are stacked together by intermolecular π-π stacking, and so the driver molecules themselves.