Chemical vapor deposition wafer boat

A chemical vapor deposition apparatus comprising a vapor deposition chamber having a gas inlet means positioned in the upper portion of the chamber for introducing gases into the chamber and a gas outlet means positioned in the lower portion of the chamber for removing gases from the chamber, a cylindrical wafer boat means positioned between the gas inlet means and the gas outlet means for supporting a plurality of wafers in an evenly spaced, upright orientation, the boat means comprising a cylinder having closed ends and comprised of mutually engaging upper and lower hemicylinders, the upper hemicylinders having diffusion zones with gas flow passageways therein in the ends and in zones within from 0.degree. to 75.degree. from a horizontal plane through the cylindrical axis and from 0.degree. to 15.degree. from a vertical plane through the cylinder axis, the remainder of the hemicylinder wall being baffle areas without gas flow passageways positioned between the gas inlet means and interior of the boat means, the ends and sidewall of the lower hemicylinder comprising a gas diffusion zones with gas flow passageways therein, the gas flow passageways comprising from 0.5 to 80 percent of the surface area of the respective gas diffusion zones.