A module assembly includes an adapter substrate with at least one cavity and a surface mounted die mounted on a top surface of the adapter substrate. The first cavity extends through the adapter substrate and has at least one first side wall. A first metallization layer is provided within the cavity. A first recessed die is attached to the first metallization layer and mounted within the cavity such that the first recessed die is at least partially recessed into the first cavity and surrounded by a gap filler that resides between side portions of the first recessed die and the at least one first side wall. The top surface of the gap filler is flush with the top surface of the adapter substrate and a top surface of the first recessed die.