Abstract: A chemical vapor deposition wafer boat for supporting a plurality of wafers in an evenly spaced, upright orientation perpendicular to the axis of the boat comprises a cylinder having closed ends and comprised of mutually engaging upper and lower hemicylinders. The upper hemicylinder has diffusion zones with gas flow passageways therein in the ends and zones within from 0 to 75 and within from 0 to 15 degrees from a vertical plane through the cylinder axis. The remainder of the hemicylinder wall and the ends are baffle areas without gas flow passageways. The ends and sidewall of the lower hemicylinder comprise gas diffusion zones. The gas flow passageways comprise from 0.5 to 80 percent of the surface area of the respective gas diffusion zones.