PURPOSE: To improve the yield of production by interposing a specific ring between a mask and a pellicle frame.

CONSTITUTION: The annular cushion ring 13 consisting of, for example, silicone rubber which has elasticity and is stable to UV light is interposed between the mask 11 and the frame 12a of the pellicle 12 and the pellicle 12 is pressed to the mask 11 in tight contact therewith by a tightening means 14. The intrusion of dust, oil mists, etc., into the hermetic space enclosed by the pellicle 12 and the ring 13 is then prevented and the ring 13 deteriorated in properties by UV rays is prevented from becoming the source for dust generation. The pellicle 12 which prevents the sticking of dust to the mask 11 over a long period of time is mounted to the mask as the pellicle is formed in such a manner and, therefore, semiconductor devices are produced at the good yield.