A memory device includes a substrate, first semiconductor fin, second semiconductor fin, first gate structure, second gate structure, first gate spacer, and a second gate spacer. The first gate structure crosses the first semiconductor fin. The second gate structure crosses the second semiconductor fin, the first gate structure extending continuously from the second gate structure, in which in a top view of the memory device, a width of the first gate structure is greater than a width of the second gate structure. The first gate spacer is on a sidewall of the first gate structure. The second gate spacer extends continuously from the first gate spacer and on a sidewall of the second gate structure, in which in the top view of the memory device, a width of the first gate spacer is less than a width of the second gate spacer.