Characteristics of submicron MOS varactors

An experimental study of the capacitive parameters of submicron accumulation-mode MOS varactors is reported. Varactors are studied as a function of channel length and width. As the device channels are scaled to smaller and smaller dimensions to achieve higher frequency circuits, the capacitance tuning range decreases because of a relative increase of fixed capacitance. At the same time, the Q-factor of the varactor increases, thus requiring the circuit designer to choose the best gate length to optimize both parameters.