A technology for reducing distance between adjacent pixel electrodes to smaller than the limit set by conventional process margin and also preventing adjacent pixel electrodes from being short circuited is provided.In a manufacturing method of a semiconductor device according to the invention, a first and a second TFTs 11 and 12 are formed over a substrate 10; an insulating film 13 is formed above the TFTs; a resist mask 14 for covering an area between adjacent pixel electrode formation areas is formed; the insulating film is formed by wet etching using the resist mask 14 as a mask, thereby forming a projection 13b provided with a surface having curvature or an inclined surface, which is disposed between the adjacent pixel electrode areas over the insulating film; a conductive film 15 is formed over the insulating film; and a conductive film about an upper part of the projection is polished and removed by CMP, thereby insulating the adjacent pixel electrodes by the projection as well as forming pixel electrodes 15a and 15b formed with the conductive film over the base insulating film.