Transparent conductive oxide (TCO) materials have attracted tremendous research interests for integrated photonics and nanophotonic devices in recent years due to the extraordinary perturbation to the refractive indices achieved either through oxygen vacancy doping or electrical gating. In addition, high quality TCO materials can be deposited using DC- or RF-sputtering on various substrates. Therefore, TCO materials promise unprecedented potentials for heterogeneous integration with silicon photonic integrated circuits (PICs) and nanophotonic platforms. In this talk, I will review recent research progress in my group for the development of TCO-gated silicon photonic devices to achieve ultra-high energy efficiency, high speed photonic devices, including photonic crystal nanocavity modulators and microring resonators with ultra-large E-O tuning efficiency. We also achieved 5Gbit/s E-O modulation speed and will also discuss the strategy to further improve the energy efficiency to atto-joule/bit and implement large-scale integration for data centers. TCO based metasurface devices will also be discussed with envisioned applications in optical filtering and beam control.