A method of manufacturing a semiconductor device includes forming a lower metal layer, forming an interfacial oxide film on the lower metal layer, providing a metal precursor on the interfacial oxide film at a first pressure to adsorb the metal precursor into the interfacial oxide film, performing a first purge process at a second pressure to remove the unadsorbed metal precursor, the second pressure lower than the first pressure, providing an oxidizing gas at the first pressure to react with the adsorbed metal precursor, performing a second purge process at the second pressure to remove the unreacted oxidizing gas and form a dielectric film, and forming an upper metal layer on the dielectric film.