1. Integrated Circuit Devices Professor Ali Javey Summer 2009 MOSFETs Reading: Chapters 17 & 18

2. The First Transistor

3. 1956 Physics Nobel Prize

4. Invention of the Field-Effect Transistor In 1935, a British patent was issued to Oskar Heil. A working MOSFET was not demonstrated until 1955.

6. Today’s MOSFET Technology Gate oxides as thin as 1.2 nm can be manufactured reproducibly. Large tunneling current through the oxide limits oxide-thickness reduction.

7. Introduction to the MOSFET Basic MOSFET structure and IV characteristics

8. Introduction to the MOSFET Two ways of representing a MOSFET:

10. Complementary MOSFETs (CMOS) When V g = V dd, the NFET is on and the PFET is off. When V g = 0, the PFET is on and the NFET is off. NFET PFET

11. Qualitative discussion: n-MOSFET V G > V T ; V DS  0 I D increases with V DS V G > V T ; V DS small, > 0 I D increases with V DS, but rate of increase decreases. V G > V T ; V DS  pinch-off I D reaches a saturation value, I D,sat The V DS value is called V DS,sat V G > V T ; V DS > V DS,sat I D does not increase further, saturation region.

12. Threshold voltage for NMOS and PMOS When V G = V T,  s = 2  F ; we get expression for V T. Ideal n-channel (p-silicon) device both terms positive Ideal p-channel (n-silicon) device both terms negative  Si /  ox = = 11.9 / 3.9  3  F > 0 means p-type  F < 0 means n-type

13. How to Measure the V T of a MOSFET V t is measured by extrapolating the I ds versus V gs (at low V ds ) curve to I ds = 0. V ds = 10mV I ds V gs V t

14. Quantitative I D -V DS Relationships “Square Law” ; I D will increase as V DS is increased, but when V G – V DS = V T, pinch-off occurs, and current saturates when V DS is increased further. This value of V DS is called V DS,sat. i.e., V DS,sat = V G – V T and the current when V DS = V DS,sat is called I DS,sat. ; Here, C ox is the oxide capacitance per unit area, C ox =  ox / x ox

15. I D -V DS characteristics expected from a long channel (  L << L) MOSFET (n-channel), for various values of V G