A CVD reactor/gas converter, a process for vapor deposition or gas conversion and an electrode unit are described. The CVD reactor/gas converter comprises a casing, which forms a process chamber inside and comprises one casing wall having at least two feedthroughs. At least one pair of first electrode units spaced with respect to each other, which comprise at least one contact part located in the process chamber and a connection part extending through a corresponding feedthrough in the casing wall, as well as at least one pair of spaced second electrode units completely located inside the casing are provided. An electrically conductive bridge element connects the pair of second electrode units inside the casing. In the method for vapor deposition or gas conversion, a plurality of rods and connection elements or of rod pairs connected to each other is positioned in a process chamber in such a way that two first electrode units are electrically serially connected via the rods and the connection elements or via the rod pairs and at least one pair of the second electrode units. A desired gas atmosphere is adjusted inside the process chamber, and a voltage is applied to the two first electrode units, so as to achieve a current flow through the rods and connection elements or through the rod pairs. The electrode unit is provided for use in a CVD reactor/gas converter having a casing, which forms a process chamber inside and comprises a casing wall having at least one feedthrough. The electrode unit comprises an electrically conductive contact part, an electrically conductive connection part connected to the contact part and an electrically conductive plate element having a diameter, which is larger than the diameter of the feedthroughs. The plate element is fixable to the casing wall comprising the feedthroughs from the outside in such a way, that the plate element seals a corresponding feedthrough and directly or indirectly supports the connection part of the electrode unit in an electrically conductive manner.