This text attempts to fill the gap between a general solid-state physics book and research articles by providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. The approach is physical and intuitive, rather than formal and pedantic. The book has been written with both students and researchers in mind. Its emphasis is on understanding the physical properties of Si and similar tetrahedrally co-ordinated semiconductors and the explanations are based on physical insights. Each chapter contains a collection of tables of material parameters, figures and problems. Many of these problems "lead the student by the hand" to arrive at the results.