A method of assembling semiconductor devices includes providing a structure that includes an array of conductive frame members beside an array of apertures and an array of conductive vias that are exposed at a first face and extend towards a second face. An array of semiconductor dies is positioned in the array of apertures with their active faces positioned in the first face of the structure. The assembly is encapsulated from the second face of the structure and a redistribution layer is formed on the first face of the structure and the active faces of the die. Material is removed from the back face of the encapsulated array to expose the vias at the back face for connection through a further redistribution layer formed on the back face to electronic components stacked vertically on the further redistribution layer.