This chapter deals with a brief description of the preparation of a silicon (Si) wafer, which acts as the substrate for all the integrated circuit fabricated from the wafer. It describes some special topics related to semiconductor fabrication and operation, namely, silicon-germanium technology, crystal defects, and the Si–silicon dioxide (SiO2) interface. The chapter illustrates how some of the basic processes can be used to fabricate some fairly simple devices, mainly semiconductor resistors, pn junction diodes, and semiconductor capacitors. It also describes the basic processes of CMOS fabrication, the details of which may vary depending on the intended application for the chip. In silicon-on-insulator (SOI) technology, each transistor is completely encased by SiO2. Alternative processes rely on wafer bonding. In the epitaxial layer transfer (ELTRAN) process, a wafer, referred to as the device wafer, is anodized to create two distinct, porous Si layers of different porosities.