Semiconductor devices having stacked structures and methods for fabricating the same are provided. A semiconductor device includes at least one single block including a first semiconductor chip and a second semiconductor chip stacked thereon. Each of the first and second semiconductor chips includes a semiconductor substrate including a through-electrode, a circuit layer on a front surface of the semiconductor substrate, and a front pad that is provided in the circuit layer and is electrically connected to the through-electrode. The surfaces of the semiconductor substrates face each other. The circuit layers directly contact each other such that the semiconductor chips are bonded to each other.