Metal-semiconductor nanostructures represent an important new class of materials employed in designing advanced optoelectronic and nanophotonic devices, such as plasmonic nanolasers, plasmon-enhanced light-emitting diodes and solar cells, plasmonic emitters of single photons, and quantum devices operating in infrared and terahertz domains. The combination of surface plasmon resonances in conducting structures, providing strong concentration of an electromagnetic optical field nearby, with sharp optical resonances in semiconductors, which are highly sensitive to external electromagnetic fields, creates a platform to control light on the nanoscale. The design of the composite metal-semiconductor system imposes the consideration of both the plasmonic resonances in metal and the optical transitions in semiconductors - a key issue being their resonant interaction providing a coupling regime.In this book the reader will find descriptions of electrodynamics of conducting structures, quantum physics of semiconductor nanostructures, and guidelines for advanced engineering of metal-semiconductor composites. These constituents form together the physical basics of the metal-semiconductor plasmonics, underlying many effective practical applications. The list of covered topics also includes the review of recent results, such as the achievement of a strong coupling regime, and the preservation of non-classical statistics of photons in plasmonic cavities combined with semiconductor nanostructures.