not produce a higher deposition rate but in contrast would lead to shunting of a larger amount of the power across the gap between substrate electrode 26 and the adjacent ground shield 20 this shunted power lowers the overall sputtering efficiency in accordance with the present invention the novel structure of the substrate electrode assembly 16 39 is shown schematically in fig3 the substrate electrode assembly 16 39 comprises a substrate electrode 26 39 which is adapted to have a substrate holder 28 39 mounted on one of its faces substrate holder 28 39 is designed to hold a large number of substrates 30 to be coated with a chosen material in the sputtering apparatus 10 according to one feature of the present invention the ground shield 20 39 is spaced a substantial distance from the back surface 32 39 of the substrate electrode 26 39 to form a back space 34 back space 34 is substantially filled with insulating means 36 such as a suitable ceramic material for example for electrically insulating ground shield 20 from the substrate electrode 26 39 the specific configuration of insulating means 36 is important to the operation of the sputtering apparatus 10 and to the.