The invention concerns an Metal-Semiconductor-Metal type photodetector device for detecting an incident light and comprising, superimposed on a support, reflecting means forming a first mirror for a Fabry-Perot resonant cavity, a non light-absorbing intermediate layer, an active layer made of semiconductor material absorbing incident light and an electrode grating for polarizing and collecting the detected signal. The electrode grating is arranged on the active layer and consists of parallel strips uniformly spaced by a period less than the wavelength of the incident light, the electrode grating constituting a second mirror for the resonant cavity, the optical properties of second mirror being determined by the geometrical dimensions of conductive strips. The distance separating the first mirror from the second mirror is determined to obtain between two mirrors a Fabry-Perot type resonance for the incident light.