Etching composition for selectively etching silicon nitride, etching method, and manufacturing method of semiconductor device using the same

An etching composition capable of increasing an etching selectivity for a silicon nitride over a silicon oxide and a polycrystalline silicon, the etching composition comprising:

• an inorganic acid;
• a solvent;
• and
• an additive,
• wherein the additive includes one or both of a compound containing an epoxy group and a compound containing a vinyl group, and the additive is a non-silicon-based additive,
• wherein the compound containing the epoxy group includes one or more of allyl glycidyl ether, epichlorohydrin, 1,2-epoxy-3-phenoxypropane, and 2,3-epoxypropyl benzene, and the compound containing the vinyl group includes one or both of vinyl bromide and phenyl vinyl ether, and
• wherein the etching composition has an etching selectivity of 50 or more for the silicon nitride compared to the polycrystalline silicon and an etching selectivity of 30 or more for the silicon nitride compared to the silicon oxide.