A photosensitive composition for forming a dielectric of the present invention comprising inorganic particles, an alkali developable resin and additives, wherein the additives comprise a compound having a quinonediazido group (C1), a compound containing at least two alkyletherified amino groups in the molecule (C2) and a thermal acid generator (C3), or wherein the inorganic particles comprise inorganic superfine particles (A-I) having a mean particle diameter of less than 0.05 mum and inorganic fine particles (A-II) having a mean particle diameter of not less than 0.05 mum. The composition can be calcined at low temperatures to form a dielectric layer with high dimensional precision, said layer having a high dielectric constant and a low dielectric loss. Also provided are a dielectric and an electronic part prepared from the composition.