In a manufacturing method for a semiconductor device provided with a MONOS-type FET for a non-volatile memory and high-voltage and low-voltage MOSFETs, a groove having a predetermined depth is formed in a region in which the high-voltage MOSFET on a semiconductor substrate is formed, and an oxide film serving as a gate insulating film of the high-voltage MOSFET is formed within the formed groove by thermal oxidation. Thereafter, a gate electrode film of the low-voltage MOSFET is formed on the entire surface of the semiconductor substrate. Thereafter, a region for the MONOS-type FET is opened, the semiconductor surface of the semiconductor substrate is exposed, and a first potential barrier film, a charge storage film, and a second potential barrier film are sequentially deposited, to thereby form a charge storage three-layer film. Agate electrode film of the MONOS-type FET is formed on the formed charge storage three-layer film.