A bolometric detector of LWIR wavelengths, including: a substrate; a membrane suspended above the substrate by supporting elements; an absorbing element comprising several MIM structures each formed with a lower metal element, an upper metal element specific to each MIM structure and with a dielectric element positioned between the lower and upper metal elements; a thermometric element comprising at least one thermometric material; wherein: the membrane includes the upper metal element, the thermometric material and one portion of the dielectric element of each MIM structure, the upper metal elements of at least two MIM structure have different dimensions relatively to each other in the main plane of the membrane, and the dielectric element of each of the MIM structures includes at least one of the following materials having vibrational modes in the LWIR range: Al2O3, AlN, TiO2.