Techniques and mechanisms for providing precisely fabricated structures of a semiconductor package. In an embodiment, a build-up carrier of the semiconductor package includes a layer of porous dielectric material. Seed copper and plated copper is disposed on the layer of porous dielectric material. Subsequent etching is performed to remove copper adjacent to the layer of porous dielectric material, forming a gap separating a suspended portion of a MEMS structure from the layer of porous dielectric material. In another embodiment, the semiconductor package includes a copper structure disposed between portions of an insulating layer or portions of a layer of silicon nitride material. The layer of silicon nitride material couples the insulating layer to another insulating layer. One or both of the insulating layers are each protected from desmear processing with a respective release layer structure.