The capacitance-voltage dependence of MIS tunnel diodes has been inves
tigated and a new general expression for the forward capacitance is re
ported. The calculated 1/C-2 plot exhibits a minimum at a specific val
ue of the de voltage. This minimum position and the corresponding volt
age value are found to be sensitive to the series resistance, the insu
lator thickness and the doping concentration in the semiconductor. Kno
wing the de current and the voltage at the minimum in the 1/C-2 versus
voltage plot, the series resistance can be readily evaluated.