Patent ID: 7843029

Claim:
A semiconductor range-finding element comprising: a semiconductor layer of first conductivity type; an island-shaped buried charge-generation region of second conductivity type buried in a part of a surface of the semiconductor layer; island-shaped first and second buried charge-transfer regions of the second conductivity type buried in a part of the surface of the semiconductor layer, separated by a part of the semiconductor layer from the buried charge-generation region, configured to accumulate signal charges transferred from the buried charge-generation region; an island-shaped first buried charge read-out region of the second conductivity type buried in a part of the surface of the semiconductor layer, separated by a part of the semiconductor layer from the first buried charge-transfer region, to which the signal charges are transferred from the first buried charge-transfer region; an island-shaped second buried charge read-out region of the second conductivity type buried in a part of the surface of the semiconductor layer, separated by a part of the semiconductor layer from the second buried charge-transfer region, to which the signal charges are transferred from the second buried charge-transfer region; an insulating film covering the semiconductor layer, the buried charge-generation region, the first and second buried charge-transfer regions, and the first and second buried charge read-out regions; first and second transfer gate electrodes arranged on the insulating film, configured to electro-statically control potentials of transfer channels formed between the buried charge-generation region and the first buried charge-transfer region and between the buried charge-generation region and the second buried charge-transfer region, respectively, through the insulating film, so as to alternately transfer the signal charges to the first and second buried charge-transfer regions; and first and second read-out gate electrodes arranged on the insulating film, configured to electro-statically control potentials of transfer channels formed between the first buried charge-transfer region and the first buried charge read-out region and between the second buried charge-transfer region and the second buried charge read-out region, respectively, through the insulating film, so as to transfer the signal charges to the first and second buried charge read-out regions, wherein a light pulse reflected by a target sample enters as an optical signal in the buried charge-generation region, and in the semiconductor layer just under the buried charge-generation region, the optical signal is converted into the signal charges, and pulse signals are sequentially applied to the first and second transfer gate electrodes in synchronization with the light pulse so that a distance from the target sample is measured in accordance with a distribution ratio of the signal charges accumulated in the first and second buried charge-transfer regions.