PURPOSE: To form a guard ring by self-alignment by forming a void between a Schottky metal and insulating film and a groove below the void and filling the void and groove with an insulator.

CONSTITUTION: After etching an insulating film 4 with a hydrofluoric acid-based etchant from an opening 50 by using a photoresist 5 as a mask, a metallic layer 60 (Schottky metal 6) composed of titanium is formed. As a result, a void 7 is formed between the side wall of the insulating film 4 forming the opening 50 and that of the metallic 6 formed in the opening 50. Then a groove 8 is formed by performing reactive ion etching through the void 7 and a polyimide resin 90 is applied to the surface of the insulating film 4 until the surface of the resin 90 becomes flat so as to fill up the groove with the resin 90. The filling of the fine groove 8 with the resin 90 is performed in such a way that, after applying the resin 9, the periphery of the groove 8 is evacuated to a vacuum so as to remove air from the groove 8, and then, the periphery is returned to the atmospheric pressure. Then, the resin 90 is removed by oxygen ashing until the metal 6 is exposed. As a result, a guard ring 9 can be formed by using the resin 90 filling the groove 8 as an insulator.