Consider the following statements— 1. The threshold voltage

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Consider the following statements—
1. The threshold voltage (V_T) of a MOS capacitor decreases with increase in gate oxide thickness.
2. The threshold voltage (V_T) of a MOS capacitor decreases with increase in substrate doping concentration. Which of the statements given above are correct.

1. 1 is FALSE and 2 is TRUE
2. Both 1 and 2 are TRUE
3. Both 1 and 2 are FALSE
4. 1 is TRUE and 2 is FALSE

Correct Option: A

The threshold voltage of N-channel MOSFET is expressed by

V_TN =		\|Q’_SD(max)\|	-	Q’_ss	+ φ_ms + 2φ_fp
		C_ox		C_ox

Where, V_TN = Threshold voltage for N-MOSFET
Q’_ss = Electronic charge perunit area
φ_ms = Work function difference
_φfp = Surface potential

e = Charge of electron
∈_s = Permitivity
N_a = Acceptor ion concentration

C_ox =	∈_ox
	t_ox

t_ox = gate oxide thickness
Thus on increasing gate oxide thickness. C_ox decreases which increase threshold voltage, V_TN.
And the threshold voltage V_TN of a MOS capacitor with increase in substrate doping concentration increases,
since VTN α √N_a
Hence alternative (A) is the correct choice.