Question

Q2. a) Draw the cross-sectional view of ann channel MOS transistor. Label the necessary parts (L, W, toi, D,G,S, etc.) Give appropriate values for L, W, tox. (10 p) b) Explain, how an n-channel enhancement mode MOS transistor operates. (10p)

Answer 1

Cross sectional view of n-channel MOS transistor.approximate values for Z = 0.1 to 3 mu m w = 0.2 to 100 mu m t_ox = 2 to 50nm enhancement mode transistor is the one in which channel is formed by applying appropriate gate voltage. An n channel Mos consists of p type substrate, source and drain are of n type and hence channel formed is of n type so the voltage applied to gate is to be positive. operation with no gate voltage: - when gate voltage = 0, no channel is formed and hence current through the channel = 0 operation with small vgs: - when small amount of vgs is applied the holes in p - type substrate are repelled and electrons which are minority carriers in p - type substrate are attracted towards gate when vgs and small vds is applied: - when vds along with vgs is applied the electrons in p - type substate and electrons in drain and source are also