Solid-state image pickup device and fabrication method thereof

DETAILED DESCRIPTION An object of the present invention is to provide a solid-state image pickup device intended to increase the accumulated charge capacity, increase the area of a light receiving portion, and prevent a reduction in actual charge amount due to variations in processed dimension between transfer electrodes, and a method of fabricating the solid-state image pickup device.
To achieve the above object, according to a first aspect of the present invention, there is provided a solid-state image pickup device including: a plurality of light receiving portions arranged in a matrix; and a vertical transfer register which is four-phase driven by transfer electrodes of a three-layer structure, said vertical transfer register being provided for each of columns of said light receiving portions; wherein those, formed by the first layer, of said transfer electrodes are composed of two kinds of transfer electrodes alternately arranged in a charge transfer direction.
With this configuration, of the transfer electrodes of the vertical transfer register which is four-phase driven, the first and third transfer electrodes formed by the first layer are alternately arranged; the second transfer electrodes formed by the second layer are each arranged between the first and third transfer electrodes in such a manner as to be laid across them; and the fourth transfer electrodes formed by the third layer are each arranged between the third and first transfer electrodes in such a manner as to be laid across them.
As a result, even if there occur variations in processed dimension between the first and third transfer electrodes of the first layer, the length of the two-phase transfer region composed of the first or third transfer electrode of the first layer and the second transfer electrode of the second layer is usually equalized to the length of the two-phase transfer region composed of the first or third transfer electrode of the first layer and the fourth transfer electrode of the third layer.
Accordingly, it is possible to increase the accumulated charge capacity in the vertical transfer register, and hence to prevent the reduction in actual charge amount