"Complementary Metal-Oxide Semiconductor" is a process which implements a combination of PMOS and NMOS transistors. Most current digital logic is implemented in CMOS. Its cost-effectiveness due to being so widespread means many other applications have become common as well, such as in analog design, image sensors, telecommunication, etc.

CMOS inverter

Further reading
HCMOS Design Considerations, TI Application Note SCLA007A
Moore's Law
CCD vs. CMOS Image Sensors, Wikipedia

CMOS: Circuit Design, Layout, and Simulation, R.Jacob Baker, Wiley