A physically unclonable function (PUF) cell array includes a first PUF cell arranged in a first column in a first direction and a second PUF cell arranged in a second column in the first direction. The first PUF cell includes a first set of conductive structures extending in the first and a second direction. The second PUF cell includes a second set of conductive structures extending in the first and the second direction. The first PUF cell includes a first conductive structure and a second conductive structure extending in the second direction. The second PUF cell includes a third conductive structure and a fourth conductive structure extending in the second direction. The first and third conductive structure or the second and fourth conductive structure are symmetric to each other with respect to a central line of at least the first or second PUF cell extending in the second direction.