An analytical model for intrinsic capacitances of short-channel MOSFETs

Precision characterization of intrinsic gate capacitances of small-geometry MOSFETs is needed for the design of analog, as well as some digital circuits, such as memories. A new and simple measurement technique for intrinsic MOSFET capacitances which does not require any on-chip circuitry, is applied to short channel devices. The short-channel transistor capacitance characteristics are found to deviate from those of the long-channel transistors in many aspects. An analytical model to explain the measurement results, especially the short-channel effects and above-threshold characteristics, is described. This new mode includes the mobility degradation effect, velocity saturation effect, bias-dependent fringing-field effect, as well as source/drain series resistance effect. Good agreement between the measured and simulated results is found.