The subject of semiconductor physics today includes not only many of the aspects that constitute solid state physics, but also much more. It includes what happens at the nanoscale and at surfaces and interfaces, behavior with few interaction events and few carriers --- electrons and their quasi-particle holes --- in the valence bands, the exchange of energies in various forms, the coupling of energetic events over short and long length scales, quantum reversibility tied to macroscale linearity and eventually to nonlinearities, the thermodynamic and statistical consequences of fluctuation-dissipation, and others. This text brings together traditional solid-state approaches from the 20th century with developments of the early part of the 21st century, to reach an understanding of semiconductor physics in its multifaceted forms. It reveals how an understanding of what happens within the material can lead to insights into what happens in its use. The collection of four textbooks in the Electroscience series culminates in a comprehensive understanding of nanoscale devices -- electronic, magnetic, mechanical and optical -- in the 4th volume. The series builds up to this last subject with volumes devoted to underlying semiconductor and solid-state physics.