A flame-retardant composition is obtained wherein at least one resin selected from a biodegradable resin and a plant-based resin or a PS resin is flame retarded by using a non-halogen-based flame retardancy-imparting component. First, a first oxide layer and a first nitride layer are sequentially formed on a substrate. The cap member forms an enclosed conduit between the cap member and the upper core member. A silicon film is arranged on the conductive layer.