Provided is a semiconductor device with improved performance. In a method for manufacturing a semiconductor device, after forming a gate electrode of a transfer transistor over a p-type well, a photodiode is formed in one part of the p-type well positioned on one side with respect to the gate electrode. Then, a cap insulating film including silicon and nitrogen is formed over the photodiode before implanting impurity ions for formation of an n-type low-concentration semiconductor region of the transfer transistor, into the other part of the p-type well positioned on a side opposite to the one side with respect to the gate electrode.