The concept and design of a new chemical vapor deposition(CVD) reactor is presented for both epitaxial and nonepitaxial film deposition in semiconductor processing. The reactor is designed in such a way than a stagnant semiconductor source fluid of uniform concentration is provided for the film deposition without causing free or forced convection. the supply of the source gas for the deposition is by diffusion through a porous material such as quartz or graphite. Compared to the low pressure CVD(LPCVD) reactor with mounted wafer configuration, the new reactor should give a better film thickness uniformity and about in order of magnitude reduction in the amount of the source gas required. Further, at least for polycrystalline silicon deposition, the deposition rate can be much higher than is currently practiced with the LPCVD reactor. Design equations for the reactor are given. Details on the design for the polycrystalline silicon deposition are also given.