A method of forming a storage capacitor in an IPS liquid crystal display device is proposed, and a technique of forming a pixel region having a high aperture ratio is provided. An anodic oxidation process at an applied voltage/voltage supply time ratio of 11 V/min is performed for insulating films used in each circuit of an electro-optical device, typically an IPS method LCD, in particular for the surface of a common electrode formed on a resin film. The amount of formation of the extra anodic oxide film can be reduced by covering with an anodic oxide film, and a liquid crystal display device with high reliability and having an electrode with superior adhesion can be manufactured.