A semiconductor device includes a first semiconductor chip comprising a first metallic structure, a top surface, and a bottom surface, a second semiconductor chip comprising a second metallic structure, wherein the second semiconductor chip is bonded with the first semiconductor chip on the bottom surface, a conductive material connecting the first metallic structure and the second metallic structure, wherein a portion of the conductive material is inside the first semiconductor chip and the second semiconductor chip, and a dielectric layer disposed surrounding the portion of the conductive material.