US Patent 7262445 Charge transfer device and solid-state image pickup device

In a charge transfer device which has many two-layered transfer electrodes, 8L disposed along a charge transfer direction X above a transfer channel is driven with two-phase driving pulses supplied to the transfer electrodes of the second layer, the transfer channel below the last-stage transfer electrode disposed at the last stage of the charge transfer direction X is constructed to have three-step potential, and the potential is set to be stepwise deeper from the upstream side to the downstream side in the charge transfer direction X.