A method for manufacturing a semiconductor structure is provided. The method includes forming a transistor over the first wafer; bonding a first wafer to a second wafer; trimming an edge region of the first wafer along a circular trimming path, wherein a center of the circular trimming path is offset from a center of the second wafer in a top view; after trimming the edge region of the first wafer, thinning down the first wafer; and after thinning down the first wafer, forming a backside conductive feature electrically connected to the transistor.