Consider the low frequency C_lf/C_ox versus CG curve in figure 1. It is for a MOS capacitor with a p-type substrate (N_A = N_A1), a metal gate and V_FB = 0. Draw the C_if/C_Cox versus V_G curve for the device if the metal gate is replaced with a p-type poly-Si gate doped to N_A = N_A1. Explain your answer.

Figure 1. lf CV characteristics of a MOS capacitor

The subthreshold ID-VG curves of a MOSFET are shown in Figure 2 before and after stressing the device. Determine the interface trap density change ΔD_it (in cm^-2eV^-1) induced by the stress. T = 300K, ε_ox = 3.9, t_ox = 10 nm.

Figure 2. Transfer characteristics of a MOSFET before and after stress

You may find the following useful: ?D_it = C_ox/2.3kT.(1/(slope before)-1/(slope after))

Why do the low frequency and high frequency CV curves differ in inversion?

Using the transfer characteristics shown in Figure 3 (VD = 2V; W/L = 10:1). Calculate the following:

The threshold voltage

The field effect mobility

Figure 3. Transfer characteristics of a TFT