Abstract: A plasma reactor for PECVD treatment of large-size substrates according to the invention comprises a vacuum process chamber as an outer chamber and at least one inner reactor with an electrode showerhead acting as RF antenna, said inner reactor again comprising a reactor bottom and a reactor top, being sealingly connected at least during treatment of substrates in the plasma reactor and separated at least during loading/unloading of the substrates. Further embodiments comprise a sealing for said reactor to/bottom and a suspender for the RF antenna/electrode showerhead.