PURPOSE: To obtain the uniformity in film thickness and to decrease the attachment of dust by providing an inert gas jetting port for shielding atmosphere in a region surrounding reaction-gas jetting port at a dispersion head, and providing an exhausting port which controls the exhausting amounts of the inert gas and the excessive reaction gas and exhausts said gases.

CONSTITUTION: A jetting port 8 for jetting N2 type inert gas 7 is provided at a region surrounding a reaction gas jetting port 6 at a dispersion head 5. An exhaust port 9 is provided at the outside. The amount of the exhaust gas is managed and controlled with a manometer 11 through a valve 10. The air is shielded with a N2 jetting port 8, and the balance of the amount of the exhaust gas is established. Thus the film thickness in a susceptor 1 can be made uniform.