A capacitive switching behavior is observed in a Si₃N₄/p-Si-based metal–insulator–semiconductor (MIS) structure due to the electron tunneling at the Si₃N₄/p-Si interface. A BiFeO₃ (BFO) layer is deposited on Si₃N₄/p-Si by pulsed laser deposition technique to obtain the memcapacitive effect as the distribution of positive charges in the Si₃N₄ layer can be stabilized by the polarization charge of the ferroelectric BFO coating layer. The capacitive switching behavior of the Al/BFO/Si₃N₄/p-Si/Au MIS structure is also sensitive to both intensity and wavelength of the illumination, which offers the possibility to create a photodetector for both intensity and color detection. Thus, the presented device has the potential application for future information storage and visible light communications. As an example, a photocapacitive demodulator with capability of decoding both wavelength and intensity information of the incident light is demonstrated.