An accurate measurement and extraction method of gate to substrate overlap capacitance [MOSFETs]

Gate-to-bulk overlap capacitance (CGBO) cannot be ignored for long gate channel MOSFETs that are used for various I/O and analog circuits. We present a simple and yet accurate CGBO measurement and extraction by using a group of MOSFETs. Dedicated test structures using 0.18 /spl mu/m shallow trench isolation technology were fabricated for the purpose. The effect of CGBO has been successfully analyzed by comparing the measured and simulated time period delay of ring oscillators.