Patent ID: 8771418

Claim:
A substrate-processing apparatus comprising: a lower chamber having an open space on an upper side; an upper chamber disposed on the upper side of the lower chamber; an inner space defined by the lower chamber and the upper chamber, in which a process for processing a substrate is performed; a shower head disposed in a lower portion of the upper chamber and having injection holes to supply a reaction gas toward the inner space; a buffer space defined by the upper chamber and the shower head therebetween; a gas supply port formed in the upper chamber to supply the reaction gas into the buffer space; a diffusion unit disposed in the buffer space to control a flow of the reaction gas supplied through the gas supply port, the diffusion unit including a block plate having a circular plate shape and spaced from a bottom surface of the upper chamber, sidewalls disposed on a bottom surface of the block plate and protruding from the bottom surface of the block plate, the sidewalls having a predetermined width and height and supporting the block plate on the shower head, a plurality of diffusion areas defined by the sidewalls and the block plate in a space between the block plate and the shower head, a plurality of diffusion holes formed in the block plate corresponding to all of the plurality of diffusion areas, and allowing all of the plurality of diffusion areas to communicate with the gas supply port; and a plurality of diffusion plates separated from the block plate and having connection holes, each of the diffusion plates having a same shape as a corresponding one to of the diffusion areas, at least one of the diffusion plates being selectively and detachably inserted into the diffusion areas.