PURPOSE: To prevent the increase of a dark current of a photodiode by providing a barrier layer between a reading shift register and the photodiode.

CONSTITUTION: The n type diffusion layers 11 and 12 forming a base, the p type diffusion layers 20 and 30 forming an emitter, and p type diffusion layers 21 and 31 and the n type diffusion layers 41 and 51 are formed on an n type semiconductor substrate 1. Thus a plasma coupled device PCD is obtained. In adition, p type diffusion layers 23, 33, 22 and 32 are formed together with n type diffusion layers 42, 43, 52 and 53. The layers 23 and 33 function as a photodiode. The output terminals 40 and 50 of the PCD are connected to layers 43 and 53 respectively. When the PCD is turned on, the electric charge stored to the photodiodes 23 and 33 is delivered to layers 42 and 52. A deep N+ diffusion layer 2 is formed between the PCD and the diodes 23 and 33 as a barrier layer. Thus no positive hole flows while the PCD is kept on state. In such a way, a dark current is reduced.