A transparent electrode composed of ITO(indium-tin oxide), an insulating layer composed of ZrSiN, an underlayer composed of MgS with a thickness of 100 to 300 nm, a light emitting layer composed of Mg.sub.1-xCa.sub.xS, and an insulating layer composed of ZrSiN are formed in this order on a glass substrate. Electrodes composed of Al are formed on the insulating layer. The underlayer is formed by sputtering with the substrate temperature set to room temperature. The light emitting layer is formed by sputtering with the substrate temperature set to not lower than 100.degree. C.