CMOS stands for Complementary Metal Oxide Semiconductor (CMOS) Field Effect Transistor. It is a prominent logic family where in a digital function is implemented as a combination of PULL UP and PULL DOWN network. It is called complementary MOS because generally, PULL UP and PULL DOWN networks are complements of each other. For example, CMOS NAND will have 2 NMOS in SERIES in PULL DOWN NETWORK and 2 PMOS in PARALLEL in PULL UP Network.