A high resistance re-grown layer is disposed around an optical device having a mesa structure. Thus, a mesa portion having a plane direction that appears in etching of a circular main structure is coated with the re-grown layer. Because of this coating, it is possible to reduce the capacitance in this portion as well as to avoid the risk of disconnection with respect to all the wiring directions. The thickness of the re-grown layer can be set to be equal to the thickness of the main structural part. Particularly, when a conductive substrate is used, a substantial reduction effect of parasitic capacitance can be expected from a combination with plural dielectric films.