An electro-optical waveguide modulator device includes a seed layer on a substrate, the seed layer having a first crystallographic plane aligned with a surface of the seed layer, an electro-optical channel extending in a first direction on the seed layer and having a second crystallographic plane aligned with the surface of the seed layer, an insulator layer on both sides of the electro-optical channel on the substrate in a second direction perpendicular to the first direction, an electrode barrier layer on the electro-optical channel and the insulator layer, and one or more of electrodes extending in the second direction. The seed layer and the insulator layer each comprise material having a refractive index that is lower than the electro-optical channel.