We have developed a multimodal CMOS sensing device to detect fluorescence image and electrical potential for neural activities in a mouse deep brain. The device consists of CMOS image sensor with on-chip electrodes and excitation light sources, all of which are integrated on a polyimide substrate. The novel feature of this device is its embedded on-chip electrodes which are partially transmit incident light so that the whole image can be acquired by the sensor. We have demonstrated the CMOS sensor device successfully operates in hippocampus area of an anesthetized mouse.