The invention provides an inorganic powder-containing resin composition capable of forming a dielectric layer having high light transmittance and excellent in surface smoothness. The invention also provides a film-forming material layer, a transfer sheet and a dielectric layer, which comprise the composition, a method of producing a substrate having a dielectric layer formed thereon, and a substrate having a dielectric layer formed thereon. The inorganic powder-containing resin composition comprises inorganic powder, a binder resin, and a phosphorus compound represented by formula (1): ##STR00001## wherein R.sup.1, R.sup.2 and R.sup.3 independently represent H, an alkyl group, an alkylaryl group, NH.sub.4.sup.+ (ammonium) or --(CH.sub.2CH.sub.2O).sub.n--R.sup.4, wherein n is 1 to 15, and R.sup.4 represents H, an alkyl group, an alkylaryl group or a (meth)acryloyl group.