Device and method for producing dielectric layers in microwave plasma

A microwave plasma device, comprising at least one electrode (21, 22, 23) which is connectable to a microwave generator (20), wherein the at least one electrode (21, 22, 23) comprises a coaxial inner conductor (21) made from electrically conductive material as well as a coaxial outer conductor (22) made from electrically conductive material, which at least partially surrounds the coaxial inner conductor and is spaced therefrom;

• wherein the coaxial outer conductor (22) comprises in its longitudinal direction at least one first region (31), in which the coaxial outer conductor completely surrounds the coaxial inner conductor, and at least one further region (32), in which the coaxial outer conductor is formed such that it tapers or narrows, in particular in a constant manner, from said first region (31), and thus surrounds the coaxial inner conductor (21) less and less, such that microwave radiation generated by the microwave generator (20) may exit from the at least one further region (32) substantially perpendicular to the longitudinal axis of the coaxial inner conductor (21), when the at least one electrode (21, 22, 23) is connected to the microwave generator (20).