Image Number 5 for United States Patent #7605411.
An HCCD includes a channel 21 that transfers electric charges in an X direction, a channel 25 that transfers the electric charges in a Z1 direction, a channel 23 that transfers the electric charges in a Z2 direction, and a channel 22 that connects the channels 23, 25 to the channel 21. The following relation is satisfied in impurity concentration of the channels: channel 21 channel 22 channel 23, 25. A fixed DC voltage is applied to branch electrodes 12a, 12b above the channel 22. The channel 22 has protrusion portions 19 that protrude inward from an outer circumference, which connects T1 and T2, and an outer circumference, which connects T3 and T4. The protrusion portions 19 causes charges below the transfer electrode 11b to move near the center of the channel 22 in a Y direction. Thereby, the travel distance of the charges in the channel 22 is reduced.