Provided is a stacked semiconductor device including a first flexible layer and a second flexible layer combined together, serving as a flexible substrate body being bent somewhere such that a surface of the first flexible layer itself is face-to-face clipped, two semiconductor chips each embedded in the flexible substrate body, and an adhesive layer sandwiched in a gap between the face-to-face surface of the first flexible layer. The active surface of each of the semiconductor chips has plurality of electrode pads thereon electrically connected to a first circuit layer on the second flexible layer. The semiconductor chips are stacked up and embedded in the flexible substrate body, thereby reducing package height to achieve miniaturization of electronic products. A method for fabricating the stacked semiconductor device is also provided.