ISBNs: 0-471-41541-3 (Hardback); 0-471-22461-8 (Electronic)
CHAPTER 7
CMOS: Devices and Future Challenges
The information revolution has been driven largely by continued progress in integrated circuit development. To date, integrated circuits have doubled functions per chip every one and a half to two years since the 1960s. This trend, formally known as Moore's law, has paced the semiconductor industry. The most ubiquitous circuitry used for digital logic applications is CMOS, the complementary metal-oxide semiconductor. The principal component of a CMOS integrated circuit is the MOSFET, the metal-oxide semiconductor field-effect transistor. The MOSFET is the fundamental switching element used to produce digital logic in integrated circuits. MOSFET switching speed and hence circuit speed increases with miniaturization. Further improvement in computer hardware (i.e., increased speed and density) requires continued progress in miniaturization. In this chapter we examine some of the boundaries that influence the continued miniaturization of MOSFET devices.
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7.1 WHY CMOS?
We begin our discussion with a basic review of the advantages of CMOS circuitry. The fundamental principles of MOSFET device performance are reviewed in the next section. Here we discuss only that which is needed to understand why CMOS circuitry has become ubiquitous in computing hardware. There are two different general types of MOSFET devices, n-and p-channel structures. These devices are sketched in Figure 7.1.1. The basic " Section provides background material for non-ECE majors.