There is provided a chemical vapor deposition apparatus comprising a structure defining a chamber having an area for horizontal positioning of a substrate, and having chamber walls for conducting a flow of gas across a surface of the substrate, said chamber having a gas inlet extending generally laterally across the width of the chamber structure; and a gas injector abutting the chamber structure adjacent said inlet, and including a plurality of gas supply passages, a gas inlet manifold connected to each of said passages, a separately adjustable metering valve apportioning flow through each of said passages, each of said passages having an outlet portion configured to cause the gas flow through the passage to diverge laterally into an expanded gas stream separated from adjacent streams, said injector further including walls that direct the gas streams into generally flat in edge-to-edge relation towards said chamber gas inlet, said chamber inlet being without partitions dividing the streams so that an edge of any one stream can mix with an edge of an adjacent stream.