A semiconductor structure includes: a first inter-level dielectric (ILD) layer overlying a molding layer, the molding layer comprising a backside redistribution layer (RDL); a first lower transmitter electrode and a first lower receiver electrode extending on the first ILD layer and electrically coupled to the backside RDL; a first dielectric waveguide overlying the first ILD layer, the first lower transmitter electrode and the first lower receiver electrode; and a second dielectric waveguide overlying the first dielectric waveguide. A dielectric constant of the first dielectric waveguide is greater than a dielectric constant of the second dielectric waveguide.

A method of forming a semiconductor structure includes: providing a first inter-level dielectric (ILD) layer overlying a molding layer, the molding layer including a transmitter ground structure and a receiver ground structure; forming first openings through the first ILD layer to expose the transmitter and receiver ground structures; forming first lower transmitter and receiver electrodes in the first openings to be respectively coupled to the transmitter and receiver ground structures; forming a first dielectric waveguide overlying the first ILD layer, and first lower transmitter and receiver electrodes; depositing a second ILD layer overlying the first dielectric waveguide; forming second lower transmitter and receiver electrodes extending through the second ILD and respectively coupled to the transmitter and receiver ground structures; and forming a second dielectric waveguide overlying the second ILD layer and the second lower transmitter and receiver electrodes.