Device for detecting electromagnetic radiation, including: - a substrate; - at least one thermal detector, placed on the substrate; - an encapsulating structure arranged so as to define with the substrate a cavity housing said thermal detector, including at least one thin encapsulating layer extending above the thermal detector; characterized in that it furthermore includes: - at least one Fabry-Perot interference filter placed level with the encapsulating structure and away from the thermal detector, said filter being formed by first and second semi-reflective mirrors (32A, 32B) that are separated from each other by a layer called the structured layer; ∘ each semi-reflective mirror (32A, 32B) including what is called a high-refractive-index layer (33A, 33B) made of at least one dielectric or semiconductor material, said layer having a thickness equal to a multiple of the ratio of a reference wavelength comprised in a detection spectral domain of the thermal detector over four times its refractive index; ∘ the structured layer including an alternation, in a plane parallel to the plane of the substrate, of what are called high-refractive-index sections made from at least one dielectric or semiconductor material, and what are called low-refractive-index sections made from a medium the refractive index of which is lower than that of the material of the high-index sections; ∘ the high-index layer of one of said semi-reflective mirrors being at least partially formed from said thin encapsulating layer. - a substrate; - at least one thermal detector, placed on the substrate; - an encapsulating structure arranged so as to define with the substrate a cavity housing said thermal detector, including at least one thin encapsulating layer extending above the thermal detector; - at least one Fabry-Perot interference filter placed level with the encapsulating structure and away from the thermal detector, said filter being formed by first and second semi-reflective mirrors (32A, 32B) that are separated from each other by a layer called the structured layer; ∘ each semi-reflective mirror (32A, 32B) including what is called a high-refractive-index layer (33A, 33B) made of at least one dielectric or semiconductor material, said layer having a thickness equal to a multiple of the ratio of a reference wavelength comprised in a detection spectral domain of the thermal detector over four times its refractive index; ∘ the structured layer including an alternation, in a plane parallel to the plane of the substrate, of what are called high-refractive-index sections made from at least one dielectric or semiconductor material, and what are called low-refractive-index sections made from a medium the refractive index of which is lower than that of the material of the high-index sections; ∘ the high-index layer of one of said semi-reflective mirrors being at least partially formed from said thin encapsulating layer. ∘ each semi-reflective mirror (32A, 32B) including what is called a high-refractive-index layer (33A, 33B) made of at least one dielectric or semiconductor material, said layer having a thickness equal to a multiple of the ratio of a reference wavelength comprised in a detection spectral domain of the thermal detector over four times its refractive index; ∘ the structured layer including an alternation, in a plane parallel to the plane of the substrate, of what are called high-refractive-index sections made from at least one dielectric or semiconductor material, and what are called low-refractive-index sections made from a medium the refractive index of which is lower than that of the material of the high-index sections; ∘ the high-index layer of one of said semi-reflective mirrors being at least partially formed from said thin encapsulating layer.