A wafer-to-wafer stacking having a hermetic structure formed therein is provided. The wafer stacking includes a first wafer, including a first substrate and a first device layer having thereon at least one chip and at least one low-k material layer, a second wafer disposed above the first wafer and having a second substrate, and a closed structure disposed on the at least one chip and arranged inside a cutting edge of the at least one chip, wherein the closed structure is extended from one side of the first device layer far from the first substrate to the other side thereof adjacent to the first substrate.