A method for fabricating a semiconductor device is provided. The method includes: providing a first wafer having a first active surface and a first rear surface opposite to the first active surface, the first wafer comprising a first circuit formed therein; providing a second wafer having a second active surface and a second rear surface opposite to the second active surface, the second wafer comprising a second circuit formed therein; bonding the first active surface of the first wafer with the second active surface of the second wafer so as to electrically connecting the first circuit and the second circuit; thinning the second wafer from the second rear surface; and forming at least a conductive through via in the second wafer, wherein the conductive through via is electrically connected to the first circuit through the second circuit.