A memory device, a semiconductor device and their manufacturing methods are provided. One of the methods may include: providing a first die and a plurality of second dies, the first die having a first pad, each of the plurality of second dies having a second pad; stacking the plurality of second dies on the first die, the second pads and the first pad arranged in a stepwise manner, and projections of the second pads of any two adjacent second dies on the first die partially overlapped; forming a connecting hole passing through the second dies; and forming a conductive body filling the connecting hole and connecting the first pad and the second pads. This method simplifies the manufacturing process of a semiconductor device, reduces the cost thereof, and improves the production yield.