  We report on a three-waveguide electro-optic switch for compact photonic
integrated circuits and data routing applications. The device features a
plasmonic metal-oxide-semiconductor (MOS) mode for enhanced
light-matter-interactions. The switching mechanism originates from a
capacitor-like design where the refractive index of the active medium,
Indium-Tin-Oxide, is altered via shifting the plasma frequency due to carrier
accumulation inside the waveguide-based MOS structure. This light manipulation
mechanism controls the transmission direction of transverse magnetic polarized
light into either a CROSS or BAR waveguide port. The extinction ratio of 18 dB
(7) dB for the CROSS (BAR) state, respectively, is achieved via a gating
voltage bias. The ultrafast broadband fJ/bit device allows for seamless
integration with Siliconon- Insulator platforms to for low-cost manufacturing.
