A transformer or a coupled inductor device comprising: two interconnected vertical columns of conductive material extending from a substrate and embedded in a supporting structure, the two interconnected vertical columns comprising a first column and a second column spaced apart from the first column, each column comprising an inner column portion and an outer column portion concentric with the inner column portion, the outer column portion and the inner column portion each having a first end and a second end, wherein the first end of the first inner column portion and the first outer column portion each comprise an input terminal or an output terminal and the first end of the second inner column portion and the second outer column portion each comprise an input terminal or an output terminal, and wherein the second end of the first inner column portion is conductively coupled to the second end of the second inner column portion by an inner interconnecting track of conductive material, and wherein the second end of the first outer column portion is conductively coupled to the second end of the second outer column portion by an outer interconnecting track of conductive material; characterised in that the device further comprises a first magnetic layer surrounding each outer column portion and a second magnetic layer surrounding each inner column portion, wherein the first and second magnetic layers comprise a plurality of vertical laminations comprising alternating magnetic and dielectric layers, wherein the second magnetic layer is provided between each inner column portion and outer column portion. two interconnected vertical columns of conductive material extending from a substrate and embedded in a supporting structure, the two interconnected vertical columns comprising a first column and a second column spaced apart from the first column, each column comprising an inner column portion and an outer column portion concentric with the inner column portion, the outer column portion and the inner column portion each having a first end and a second end, wherein the first end of the first inner column portion and the first outer column portion each comprise an input terminal or an output terminal and the first end of the second inner column portion and the second outer column portion each comprise an input terminal or an output terminal, and wherein the second end of the first inner column portion is conductively coupled to the second end of the second inner column portion by an inner interconnecting track of conductive material, and wherein the second end of the first outer column portion is conductively coupled to the second end of the second outer column portion by an outer interconnecting track of conductive material; characterised in that the device further comprises a first magnetic layer surrounding each outer column portion and a second magnetic layer surrounding each inner column portion, wherein the first and second magnetic layers comprise a plurality of vertical laminations comprising alternating magnetic and dielectric layers, wherein the second magnetic layer is provided between each inner column portion and outer column portion. <EOS>