A semiconductor device has a first semiconductor die and conductive vias in the first semiconductor die. The conductive vias can be formed by extending the vias partially through a first surface of the first semiconductor die. A portion of a second surface of the first semiconductor die is removed to expose the conductive vias. A plurality of conductive pillars is formed over the first surface the first semiconductor die. The conductive pillars include an expanded base electrically connected to the conductive vias. A width of the expanded base of the conductive pillars is greater than a width of a body of the conductive pillars. A conductive layer is formed over a second surface of the first semiconductor die. The conductive layer is electrically connected to the conductive vias. A second semiconductor die is mounted to the first semiconductor die with a second conductive pillar having an expanded base.