The invention provides a TRIS-containing vinylic monomer which comprises one sole (meth)acryloyloxy group and a tris(trimethylsiloxy)silyl group covalently linked to the ethylenically-unsaturated group through a polyoxyethylene linker. The present invention is also related to a polymer, an actinically-crosslinkable silicone-containing prepolymer, a silicone hydrogel polymeric material, or a silicone hydrogel contact lens, which comprises monomeric units derived from a TRIS-containing vinylic monomer of the invention. In addition, the invention provides a method for making a TRIS-containing vinylic monomer of the invention.