Image Number 12 for United States Patent #8084340.
A method of manufacturing a semiconductor device whereby, even in cases where ions are implanted into a shallow region of a semiconductor substrate when a deep well is formed, the influence of the ions on a MOSFET can be removed, thereby eliminating the need for increasing the chip area. A photoresist with a thickness matching the wavelength of exposure light is formed over the semiconductor substrate and then is exposed to the exposure light to form a photoresist pattern with an opening corresponding to a region for forming a first well. Subsequently, using the photoresist pattern as a mask, ions are implanted to form the first well, and after the photoresist pattern is removed, an epitaxial layer is grown over the semiconductor substrate. Consequently, the deep well is virtually located deeper in level than at the time of the ion implantation by an amount corresponding to the thickness of the epitaxial layer.