Optical waveguide element, optical modulator, optical modulation module, and optical transmission device

An optical waveguide device comprising:

• a substrate on which optical waveguides are formed;
• and
• an electrode that is formed on the substrate and has intersections crossing over the optical waveguides, wherein
• the optical waveguides are configured by protruding portions extending on the substrate,
• the intersections include an intermediate layer between the optical waveguides and the electrode crossing over the optical waveguides,
• the intermediate layer fills recess portions formed along the electrode and extending between the protruding portions of adjacent intersections of the intersections, and the intermediate layer is formed to have a thickness greater than a height of the protruding portions from a surface of the substrate so that the protruding portions and the intermediate layer filled in the recess portions are flat, and
• the intermediate layer, under the electrode, has a strip shape along an extending direction of the electrode in plan view.