Abstract: Nonvolatile memory devices, and methods of forming the same are disclosed. A memory device includes a substrate having a cell region, a low voltage region and a high voltage region. A ground selection transistor, a string selection transistor and a cell transistor are in the cell region, a low voltage transistor is in the low voltage region, and a high voltage transistor is in the high voltage region. A common source contact is on the ground selection transistor and a low voltage contact is on the low voltage transistor. A bit line contact is on the string selection transistor, a high voltage contact is on the high voltage transistor, and a bit line is on the bit line contact. A first insulating layer is on the substrate, and a second insulating layer is on the first insulating layer. The common source contact and the first low voltage contact extend to a height of the first insulating layer, and the bit line contact and the first high voltage contact extend to a height of the second insulating layer.

Abstract: A memory device includes a substrate having a cell region, a low voltage region and a high voltage region. A ground selection transistor, a string selection transistor and a cell transistor are in the cell region, a low voltage transistor is in the low voltage region, and a high voltage transistor is in the high voltage region. A common source contact is on the ground selection transistor and a low voltage contact is on the low voltage transistor. A bit line contact is on the string selection transistor, a high voltage contact is on the high voltage transistor, and a bit line is on the bit line contact. A first insulating layer is on the substrate, and a second insulating layer is on the first insulating layer. The common source contact and the first low voltage contact extend to a height of the first insulating layer, and the bit line contact and the first high voltage contact extend to a height of the second insulating layer.