A thin-film capacitive bolometer is described, which depends on a temperature sensitivity derived from electron trapping effects in thin amorphous dielectric films containing an ionic space charge. The theory of thisprocess is summarized and shown to be in good agreement with results obtained from anodized Nb(2)O(5) capacitors. The capacitive elements can be formed on thin-film supportingstructures to achieve large thermal detectivities D*. An analysis given for an optimized detector indicatesthat it is possible to reach the theoretical maximum D* at room temperature. Experimental detectors aredescribed which were fabricated from anodized Nb(2)O(5) and evaporated Al(2)O-TiO(2) capacitors. Their performance at room temperature indicates responsivities of at least 2 mV/microW, effective time constants of about 0.05 sec, and D*'s in excess of 10(9).