Most dielectric materials have very weak electro-optic properties, whereas the optical properties of some plasmonic materials may be greatly tuned, especially around their plasma frequency, where dielectric constant is transiting between positive (“dielectric state”) and negative (“metallic state”) values. In this talk, we will review some of our recent work on electro-optical modulation and introduce a new concept, photonic MOS based on “optical property inversion”. This concept may provide inspiration for the development of nanophotonic devices. While the whole paper only discusses theory and modelling, some new experimental results will be presented in the on-site talk. Throughout this report, “static dielectric constant”, ɛ, refers to material dielectric constant in the DC or radio frequency (RF) regime; “optical dielectric constant”, ε, represents material dielectric constant in the near-infrared regime. This paper was re-written based on an Arxiv file .