The invention relates to a method and a device for the plasma treatment of metal substrates or insulating substrates (3) running substantially continuously through a vacuum chamber having a treatment zone (2), the plasma being sustained by radiofrequency inductive coupling in the treatment zone (2) by means of an inductor (4) connected to a radiofrequency generator, in which the inductor (4) is protected from any contamination by the material emitted by the surface of the substrates (3) by means of a Faraday cage (7), which is positioned between the plasma and the inductor (4), and in which the Faraday cage (7) is on average electrically biassed positively with respect to the substrates (3) or with respect to a counter-electrode present in the plasma.