Introduction of MOS Capacitor

    There are three regions of MOS capacitor: accumulation, depletion, and inversion. Besides, there are two special critical points between these three conditions: flat-band and threshold as shown in the Figure 1. 

    The Figure below shows the ideal C-V curve of a n-type substrate. The red line indicates the capacitance of MOS capacitor operating in high frequency condition (normally 1 MHz), while the blue line indicates the capacitance operation in low frequency condition (normally 1 Hz). 

    The curve of p-type is the same as n-type, but the sign of the applied gate voltage is inverted.

Figure 1 C-V curve of n-type MOS capacitor [1] 

Reference:

[1] “MOS capacitor | MOS capacitance C V curve,” Electrical Engineering, [Online]. Available: http://www.electrical4u.com/mos-capacitor-mos-capacitance-c-v-curve/. [Accessed 6 February 2014].