A semiconductor package structure, comprising: a first semiconductor die having a first surface and a second surface opposite thereto; a first molding compound surrounding the first semiconductor die; a first redistribution layer structure disposed on the second surface of the first semiconductor die and laterally extending on the first molding compound; a second semiconductor die disposed on the first RDL structure and having a first surface and a second surface opposite thereto; a second molding compound surrounding the second semiconductor die; a second RDL structure that is disposed on the second surface of the second semiconductor die and laterally extends on the second molding compound; a third semiconductor die disposed on the second RDL structure and having a first surface and a second surface opposite thereto; a third molding compound surrounding the third semiconductor die; a third RDL structure disposed on the second surface of the third semiconductor die; and a first protective layer covering a sidewall of the first RDL structure, a sidewall of the first molding compound, a sidewall of the second RDL structure and a sidewall of the second molding compound; wherein the first protective layer is an extending portion of the third molding compound; the third RDL structure laterally extends on the third molding compound; wherein the semiconductor package structure further comprises a backside film disposed on the first surface of the first semiconductor die, and wherein the extending portion extends along the sidewall of the second RDL structure and the sidewall of the second molding compound; and characterised in that the extending portion extends along the sidewall of the first RDL structure and the sidewall of the first molding compound to the backside film thereby entirely covering the sidewall of the second RDL structure, the sidewall of the second molding compound, the sidewall of the first RDL structure and the sidewall of the first molding compound. a first semiconductor die having a first surface and a second surface opposite thereto; a first molding compound surrounding the first semiconductor die; a first redistribution layer structure disposed on the second surface of the first semiconductor die and laterally extending on the first molding compound; a second semiconductor die disposed on the first RDL structure and having a first surface and a second surface opposite thereto; a second molding compound surrounding the second semiconductor die; a second RDL structure that is disposed on the second surface of the second semiconductor die and laterally extends on the second molding compound; a third semiconductor die disposed on the second RDL structure and having a first surface and a second surface opposite thereto; a third molding compound surrounding the third semiconductor die; a third RDL structure disposed on the second surface of the third semiconductor die; and a first protective layer covering a sidewall of the first RDL structure, a sidewall of the first molding compound, a sidewall of the second RDL structure and a sidewall of the second molding compound; wherein the first protective layer is an extending portion of the third molding compound; the third RDL structure laterally extends on the third molding compound; wherein the semiconductor package structure further comprises a backside film disposed on the first surface of the first semiconductor die, and wherein the extending portion extends along the sidewall of the second RDL structure and the sidewall of the second molding compound; and characterised in that the extending portion extends along the sidewall of the first RDL structure and the sidewall of the first molding compound to the backside film thereby entirely covering the sidewall of the second RDL structure, the sidewall of the second molding compound, the sidewall of the first RDL structure and the sidewall of the first molding compound.