A semiconductor package includes a first semiconductor chip having a first substrate, a first insulating layer on the first substrate, and a plurality of first bonding pads on the first insulating layer, and having a flat upper surface by an upper surface of the first insulating layer and upper surfaces of the plurality of first bonding pads; and a second semiconductor chip on the upper surface of the first semiconductor chip and having a second substrate, a second insulating layer below the second substrate and in contact with the first insulating layer, and a plurality of second bonding pads on the second insulating layer and in contact with the first bonding pads, respectively, wherein the first insulating layer includes an insulating interfacial layer in contact with the second insulating layer, embedded in the first insulating layer, and spaced apart from the plurality of first bonding pads.