NOVELTY - A curable composition (4) comprises 15-95 wt.% reactive functional group-containing compound (I), polymerization initiator, and 3-83 wt.% filler chosen from silica, talc and calcined kaolin. The water-vapor permeability (at 60 degrees C and 90 %relative humidity) of a cured material (with thickness of 100 mu m and curing degree of more than 50%) of the curable composition is 25 g/m2.24 hours.atm or less.    USE - Curable composition is used as dam material for sealing semiconductor element (claimed) for organic electroluminescent module, solar cell module and liquid-crystal module.    ADVANTAGE - The curable composition has moderate viscosity and excellent handleability, provides cured material having low water-vapor permeability and excellent damp-proof property and low outgas property. The generation of curing failure can be prevented, even when the filler containing phenyl sulfide derivative as binder resin is mixed with the curable composition. The semiconductor element sealed using the curable composition has excellent reliability and durability. The deterioration of semiconductor element can be prevented.    DETAILED DESCRIPTION - A curable composition comprises 15-95 wt.% reactive functional group-containing compound of formula (I), polymerization initiator, and 3-83 wt.% filler chosen from silica, talc and calcined kaolin. The water-vapor permeability (at 60 degrees C and 90 %relative humidity) of a cured material (with thickness of 100 mu m and curing degree of more than 50%) of the curable composition is 25 g/m2.24 hours.atm or less.    R'a=reactive functional group;    R'b=halo, alkyl, haloalkyl, aryl, nitro, cyano, or hydroxy, hydroxyalkyl, acyl, amino, carboxy or sulfo (all optionally protected by protecting group);    R'c=single bond or coupling group;    m=0-4;and    n=0-10.    An INDEPENDENT CLAIM is included for semiconductor element, which is sealed using a dam material (2) and a filler, where the dam material is curable composition.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining the sealing method of the organic electroluminescent element.    Dam material (2)    Dispenser (3)    Curable composition (4)    Substrate (5)    Cathode (6)