| 摘要 |
PURPOSE:To enable to decrease the malfunction by a method wherein a surface layer is made the same conductive type as the semiconductor layer immediately thereunder, and the concentration of the surface layer is more increased than the impurity concentration of the semiconductor layer. CONSTITUTION:In one picture element in the photo diode array part of a solid- state image sensor, a P type Si substrate 71 has the impurity concentration of approx. 5X10<14>cm<-3>, and a P type well layer 72 has a higher concentration than the substrate 71, the impurity concentration of approx. 6X10<15>cm<-3>. The potential of the well 72 can be led out directly from the back surface via the substrate 71 of the same conductive type, therefore the resistance R in the transverse direction of the well 72 is eliminated accordingly CR time constant determined by the R and the capacitance C between the well and the substrate becomes the minimum, and the variation of well potentials can be decreased and made uniform. Consequently, horizontal shading due to the variation of well potentials is eliminated, and thus the dummy signal due to vertical smear can be suppressed. Also in the case of applying the semiconductor device to an N- MOS memory, the charge diffusion due to alpha rays is suppressed by a potential barrier, therefore the malfunction remarkably decreases. |
