Gas distributor with pre-chambers arranged in planes

A gas distributor for a CVD or OVPD reactor comprises two or more gas volumes into each of which opens a feed pipe for a process gas, each gas volume being connected to a plurality of corresponding process gas outlets which open into the bottom of the gas distributor. In order to increase the homogeneity of the gas composition, the two gas volumes comprise pre-chambers located in a first common plane and a plurality of gas distribution chambers each associated with a gas volume are provided in a second plane (′) adjacent to the bottom of the gas distributor. The pre-chambers and gas distribution chambers associated with each gas volume are connected with connection channels.