An integrated circuit includes at least one photodiode of the floating substrate type which is associated with a read transistor. The photodiode is formed from a buried layer lying beneath the floating substrate and an upper layer lying on the floating substrate. The upper layer incorporates the source and drain regions of the read transistor. The source and drain regions are produced on either side of the gate of the read transistor. An isolating trench is located alongside the source region and extends from the upper surface of the upper layer down to below the buried layer, so as to isolate the source region from said buried layer.