A semiconductor device that has the structure of a MOSFET with an extremely long channel and many gates, perhaps 1000, closely spaced between the source and drain electrodes. A MOS capacitor is formed between each gate and the substrate; since this capacitor is capable of storing a charge, CCDs can be used as memory devices. The CCD essentially acts as a long (high-density) shift register since, by manipulating the voltages applied to the gates, charge can be transferred from one MOS capacitor to its neighbour, and so on along the channel.

The physical structure of the device and the way in which the gate voltages are manipulated determines the number of gates needed to store one bit of information, typically two or three gates being required. Since the stored charge leaks away, CCDs must be continuously clocked, typically at a frequency of one megahertz.

CCDs are also manufactured in arrays and as they are sensitive to light they are widely used in video cameras, where they replace the vidicon tube used previously, and in other sensing applications. Both monochrome and colour arrays are available. Digital cameras rely on CCD arrays to capture the image.