A semiconductor device includes a first die, a second die, a first redistribution layer (RDL) structure and a connector. The RDL structure is disposed between the first die and the second die and is electrically connected to the first die and the second die and includes a first polymer layer, a second polymer layer, a first conductive pattern and an adhesion promoter layer. The adhesion promoter layer is between and in direct contact with the second polymer layer and the first conductive pattern. The connector is disposed in the first polymer layer and in direct contact with the second die and the first conductive pattern.