A stack-type semiconductor package includes a first semiconductor package upon which a second semiconductor package is stacked. A layer of a hardened, insulative material, e.g., a no-flow underfill (NUF) material, is disposed between, and mechanically couples the stacked first and second semiconductor packages. The NUF layer covers portions of the first semiconductor package, e.g., the semiconductor die and the substrate of the first semiconductor package, and solder balls of the second semiconductor package that are fused to the substrate of the first semiconductor package. The NUF material is applied onto the semiconductor die and substrate of the first semiconductor package before the second semiconductor package is stacked on the first semiconductor package, and substantially cures after the solder balls of the second semiconductor package are fused to the substrate of the first semiconductor package.