The present invention is related to an apparatus and a method for chemical vapor deposition (CVD) using a showerhead through which a reactive gas of at least one kind and a purge gas is injected over a substrate on which a film is growing. A plural number of reactive gas showerhead modules are laid on a purge gas showerhead module. Each reactive gas is injected from a bottom of the showerhead after flowing through the showerhead as separated, thereby preventing the reactive gases from causing homogeneous gas phase reactions and from generating unwanted particles at the inside of the showerhead. And a purge gas is injected from the bottom surface of the showerhead by forming a protective curtain, thereby suppressing diffusion of the reactive gas injected backwardly. Each reactive gas is mixed with an injection support gas which is a kind of inert gas in a mixing zone at inside of the showerhead, where the injection velocity of each reactive gas is regulated positively by the amount of the injection support gas mixed. The present invention further includes an apparatus and a method, wherein the showerhead is cooled by a cooling jacket which keeps the temperature of the showerhead at proper levels to prevent both the condensation and the thermal decomposition of the reactive gas used.