According to embodiments of the present invention, an electron device is provided. The electron device includes a support substrate, a conductive planar slow-wave structure on the support substrate, the conductive planar slow-wave structure being adapted to receive an electromagnetic wave signal for interaction with an electron beam, and a dielectric layer arrangement in between the conductive planar slow-wave structure and the support substrate, the dielectric layer arrangement being arranged on the support substrate at only one or more support substrate portions overlapping with the conductive planar slow-wave structure. According to further embodiments of the present invention, a method for manufacturing an electron device is also provided.