The invention relates to a semiconductor device comprising a charge-coupled device provided at a surface of a semiconductor body and comprising an input stage for forming charge packets in dependence upon an input signal, and a row of clock electrodes provided with connection means for applying clock voltages on behalf of the sequential storage and transport of these charge packets in an underlying charge transport channel, the input stage comprising, viewed in the charge transport direction, in order of succession an input diode, a first electrode (designated hereinafter as sample gate) and a second electrode (designated hereinafter as input gate), while the input diode is provided with a connection for applying a fixed voltage, the input gate is provided with means for applying the input signal and the sample gate is provided with means for applying a sample clock voltage for closing and interrupting the connection between the input diode and the region below the input gate.
A charge-coupled device comprising such an input stage designated as SHC2 (sample and hold circuit 2) is described in the article "A Comparison of CCD Analog Input Circuit Characteristics" by H. Wallings, International Conference on Technology and Applications of Charge-Coupled Devices, Edinburgh, September 1974, p. 13-21. This input has a linear characteristic and is moreover suitable for applications at high frequencies. In this publication the disadvantage is mentioned that the input signal should be supplied or should be attenuated in pulsatory form in order to guarantee that the charge packet below the input gate can be transferred as a whole to the storage zone below the first clock electrode. However, the aforementioned solutions also have disadvantages. For example, when the input signal is supplied in pulsatory form, this may lead to signal distortion, which may be unobjectionable for digital applications, it is true, but may be ojectionable, for example, for analog voltages. Attenuation of the signal generally leads to a disadvantageous reduction of the signal-to-noise ratio. For further background, see "IEEE Journal of S.S.C.", Vol. SC-13, No. 5, pp. 542-548 (October 1978).
The problem of incomplete charge transport from the input structure to the charge transport channel with the use of input circuits of the kind described above occurs especially in charge-coupled devices, in which the electrodes comprise a transfer part and a storage part and in which means (thicker oxide and/or, for example, additional implantation) are internally provided for inducing a potential barrier below the transfer parts. As will appear from the description of the Figures, due to this potential barrier, the range in which the input signal can vary is very small as a result of the requirement that it must be possible for the whole charge packet to be transferred.