A method for manufacturing a semiconductor device includes stacking, on a package substrate, first semiconductor chips. Each of the first semiconductor chips includes a first adhesive film. The method includes stacking, respectively on the first semiconductor chips, second semiconductor chips. Each of the second semiconductor chips includes a second adhesive film. The method includes compressing the first and second adhesive films to form an adhesive structure. The adhesive structure includes an extension disposed on sidewalls of the first and second semiconductor chips. The method includes removing the extension. The method includes forming a first molding layer substantially covering the first and second semiconductor chips. The method includes performing a cutting process on the package substrate between the first and second semiconductor chips to form a plurality of semiconductor packages each including at least one of the first semiconductor chips and at least one of the second semiconductor chips.