Embodiments relate to a semiconductor device for an image sensor method of fabricating a semiconductor device for an image sensor having a micro lens. According to embodiments, the method may include forming a lower insulating film having cavities on a substrate, forming an upper insulating film having cavities on the lower insulating film, forming a protective insulating film having metal films on the upper insulating film, forming a number of color filters having a specified pattern on the protective insulating film, forming a planarization layer having a specified curvature on the color filters to bury the color filters in the planarization layer, and forming a number of micro lenses on the planarization layer at respective positions corresponding to the color filters.