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Output: I CH 5 MOSET Physical Structure of NMOS THE FIRST In 1925 a patent for solid-state electric-field-controlled conductor was filed in Canada by FIELD-EFFECT Julius E. Lilienfeld, a physicist at the University of Leipzig, Germany. Other patent DEVICES: refinements followed in the United States in 1926 and 1928. Regrettably, no research papers were published. Consequently, in 1934 Oskar Heil, a German physicist working at the University of Cambridge, U.K., filed a patent on a similar idea. But all these early concepts of electric-field control of a semiconducting path languished because suitable technology was not available. The invention of the bipolar transistor in 1947 at Bell Telephone Laboratories resulted in the speedy development of bipolar devices, a circumstance that further delayed the development of field-effect transistors. Although the field-effect device was described in a paper by William Shockley in 1952, it was not until 1960 that a patent on an insulated-gate field-effect device, the MOSFET, was filed by Dawon Kahng and Martin Atalla, also at Bell Labs. Clearly, the idea of field-effect control for amplification and switching has changed the world. With integrated-circuit chips today containing billions of MOS devices, MOS dominates the electronics world! S o Metal G W D Oxide (SiO2) Source n region L p-type substrate (Body) Channel region O B Drain region (a) Source (S) Gate (G) Drain (D) Oxide (SiO2) Metal (thickness = tox) Channel n region n L p-type substrate (Body) Body (B) (b) Figure 5.1 Physical structure of the enhancement-type NMOS transistor: (a) perspective view; (b) cross section. Typically L = 0.03 um to 1 um, W = 0.05 um to 100 um, and the thickness of the oxide layer (tox) is in the range of 1 to 10 nm.