In this paper a unified quantum correction charge model for nanoscale single- and double-gate MOS structures is presented. Based on the numerical solution of Schrödinger-Poisson equations, the developed quantum correction charge model is mainly optimized with respect to (i) the left and right positions of the charge concentration peak, (ii) the maximum of the charge concentration, (iii) the total inversion charge sheet density, and (iv) the average inversion charge depth, respectively. For nanoscale single- and double-gate MOS structures, this model predicts inversion layer electron density for various oxide thicknesses, silicon film thicknesses, and applied voltages. Compared to the Schrödinger-Poisson results, our model prediction is within 2.5% of accuracy for both the single- and double gate MOS structures on average. This quantum correction model has continuous derivatives and is therefore amenable to a device simulator.