PURPOSE:To increase the degree of freedoms in a design by forming a photoelectron irradiating film made of a thin film of a substance selected from a group consisting of platinum, gold, palladium, chromium, nickel and tungsten corresponding to a region for radiating photoelectrons on a thin film made of an insulator. CONSTITUTION:A thin film 6 of an insulator, such as silicon dioxide, silicon nitride, boron nitride, etc., is formed on a silicon film 5 containing an impurity, a light shielding film 72 formed of a film made of platinum, gold, palladium, chromium, nickel, tungsten, aluminum, silicon, molybdenum, tantalum, titanium, etc., is formed corresponding to a region 71 which does not radiate photoelectrons on the film 6, and a photoelectron radiating film 8 formed of a thin film made of platinum, gold, palladium, chromium, nickel, tungsten, etc., is formed corresponding to a region 73 which irradiates photoelectrons at least on the film 6. The thickness of the film 6 and the thickness of the film 8 are desired to be thin. If they are respectively set to 50A or less and 150A or less, their photoelectron radiation efficiencies are improved.
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