A semiconductor package includes a package substrate, a plurality of semiconductor devices stacked on the package substrate, a plurality of underfill fillets disposed between the plurality of semiconductor devices and between the package substrate and the plurality of semiconductor devices, and a molding resin at least partially surrounding the plurality of semiconductor devices and the plurality of underfill fillets. The plurality of underfill fillets include a plurality of protrusions that protrude from spaces between each of the plurality of semiconductor devices or between the package substrate and each of the plurality of semiconductor devices. At least two neighboring underfill fillet protrusions of the plurality of protrusions form one continuous structure without an interface therebetween.