The present invention provides a crosslinkable elastomer composition, in which generation of HF under high temperature conditions is reduced, the decrease in weight to both NF.sub.3 plasma treatment and O.sub.3 treatment in the semiconductor manufacturing process is small and generation of foreign substances (particles) in these treatments is suppressed significantly. Specifically, the present invention relates to a crosslinkable elastomer composition comprising a crosslinkable elastomer and a filler having a specific surface area of at least 0.5 m.sup.2/g and containing a synthetic polymer having a thermally and chemically stable aromatic ring in the main chain, a crosslinkable elastomer composition comprising a crosslinkable elastomer and nonoxide ceramics and a crosslinkable elastomer composition wherein the decrease in weight by NF.sub.3 plasma irradiation is at most 0.20%.