Integrated circuit devices having optimized fin critical dimension loading are disclosed herein. An exemplary integrated circuit device includes a core region that includes a first multi-fin structure and an input/output region that includes a second multi-fin structure. The first multi-fin structure has a first width and the second multi-fin structure has a second width. The first width is greater than the second width. In some implementations, the first multi-fin structure has a first fin spacing and the second multi-fin structure has a second fin spacing. The first fin spacing is less than the second fin spacing. In some implementations, a first adjacent fin pitch of the first multi-fin structure is greater than or equal to three times a minimum fin pitch and a second adjacent fin pitch of the second multi-fin structure is less than or equal to two times the minimum fin pitch.