A semiconductor device of an embodiment can prevent nitriding of the lower-layer insulating film and oxygen diffusion from the upper-layer insulating film, so as to minimize the decrease in charge capture density. This semiconductor device includes a semiconductor layer, a first insulating film provided on the semiconductor layer, a nitrogen-added amorphous silicon layer formed on the first insulating film, a first silicon nitride layer formed on the amorphous silicon layer, and a second insulating film formed above the first silicon nitride layer.