This paper describes the sensitivity to capture fingerprint images on a capacitive fingerprint sensor LSI with a grounded (GND) wall structure. We investigated the sensing characteristics of the fingerprint sensor LSI with the GND wall structure in comparison with that of the conventional planar structure. For the analysis, we proposed circuit models based on the GND wall and the planar structure that take account of the finger's resistance, and calculated numerically the sensing characteristics. The analysis revealed that the resistance of the finger degrades the sensitivity and the GND wall structure provides a high sensitivity because it suppresses the finger's resistance. The experimental results confirmed that the proposed models are appropriate and clarified the effect of the GND wall structure on fingerprint images. Therefore, it is concluded that a fingerprint sensor LSI with the GND wall structure achieves a high sensitivity in capturing clear fingerprint images.