An inductor includes a core and a conductive spiral wound around the core. The core includes a buffer layer, an etch stop layer, and a core material layer sequentially stacked. The core material layer includes a ferromagnetic material. A total area of a vertical projection of the core material layer is smaller than an area occupied by the etch stop layer. The vertical projection of the core material layer falls entirely on the etch stop layer. The etch stop layer horizontally protrudes with respect to the core material layer.