A charge-coupled device has a first P-type well layer which forms a charge transfer section and a second P-type well layer which forms a floating diffusion layer section and within which the first P-type well layer is formed. The second P-type well layer below the floating diffusion layer section has an impurity concentration lower than that of the first P-type well layer whereby a depletion layer formed therein by a PN-junction flares in the direction to the second P-type well layer. With this arrangement, it is made possible to reduce the floating diffusion capacitance and to maintain a large output voltage with respect to a signal electron charge.