Disclosed is a semiconductor device including a bottom electrode, a dielectric layer, and a top electrode that are sequentially disposed on a substrate. The dielectric layer includes a hafnium oxide layer including hafnium oxide having a tetragonal crystal structure, and an oxidation seed layer including an oxidation seed material. The oxidation seed material has a lattice constant having a lattice mismatch of 6% or less with one of a horizontal lattice constant and a vertical lattice constant of the hafnium oxide having the tetragonal crystal structure.