This textbook offers a comprehensive introduction to the basic principles ruling the working mechanism of the most common solid-state electronic devices. It covers the physics of semiconductors and the properties of junctions of semiconductors with semiconductors, metals, and insulators. The exposition makes a minimal use of quantum mechanics concepts and methods. On the other hand, it avoids the pure phenomenological description of the properties of electronic devices. Thus, using a semi-classical approach the book provides a rigorous treatment of the subject. The book is addressed to undergraduate students of scientific and technological faculties as well to professionals who wish to be introduced to the basic principles of electronic devices.