An image sensor device includes a digital pixel that includes a photo detector, a comparator, and a memory circuit, a pixel driver that controls the digital pixel, and a digital logic circuit that performs a digital signal processing operation on a digital signal output from the digital pixel. The photo detector and a first portion of the comparator are formed in a first semiconductor die, a second portion of the comparator, the memory circuit, and the pixel driver are formed in a second semiconductor die under the first semiconductor die, and the digital logic circuit is formed in a third semiconductor die under the second semiconductor die.