A metal–ferroelectric–semiconductor (MFS) structure was used as a nonlinear capacitor in a series resonance circuit. The following materials were used as components of the MFS structure: aluminium as the metal electrode, Bi ₄ Ti ₃ O ₁₂ film as the ferroelectric, and p-type silicon as the semiconductor. The system was driven by a single frequency at suitably chosen amplitudes. Besides the sequences of period-doubling bifurcations which were already observed in the series resonance circuit with a pure ferroelectric capacitor, we found regions with torus-doubling bifurcations by varying the frequency of the driving voltage at suitably high amplitudes. Comparing the behaviour of the series resonance circuit with a pure ferroelectric capacitor and with the MFS structure, we attribute the reason for the new effect of torus doubling to the properties of the ferroelectric–semiconductor boundary layer.