Abstract: A method for producing polycrystalline semiconductor material layers of, in particular, silicon by vapor phase deposition in a plasma reactor. Hydrogen in its activated condition is supplied to the reaction gas in the reactor through an additional gas feed. In an embodiment, the activation proceeds with a glow cathode located in the hydrogen gas feed. The method enables the deposition of uniform polycrystalline semiconductor material layers at substrate temperatures of from between approximately 100.degree. to about 450.degree. C. The deposition can be implemented onto normal glass substrates in a plasma reactor having a simple structure. The method can be used for the manufacture of transistors through thin-film technology.