A method for atomizing a precursor liquid for vapor generation and thin film deposition on a substrate. The precursor liquid is atomized by a carrier gas to form a droplet aerosol composed of small precursor liquid droplets suspended in the carrier gas. The droplet aerosol is then heated to form vapor, producing a gas/vapor mixture that can be introduced into a deposition chamber to form thin films on a substrate. The liquid is introduced into the atomizing apparatus in such a manner as to avoid excessive heating that can occur or lead to the formation of undesirable by-products due to material degradation as result of thermal decomposition. The method is particularly suited for vaporizing high molecular weight substances with a low vapor pressure that requires a high vaporization temperature for the liquid to vaporize. The method can also be used to vaporize solid precursors dissolved in a solvent for vaporization.