A memory array includes a first memory cell configured to store data, a second memory cell configured to store data and a bit line extending along the first direction, and being over the first memory cell and the second memory cell. The first memory cell and the second memory cell are arranged along a first direction in a first column of memory cells. The bit line includes a first conductor extending in the first direction and being in a first conductive layer, and a second conductor extending in the first direction and being in a second conductive layer different from the first conductive layer.