A semiconductor device is disclosed. A conductive pillar for electrically connecting a semiconductor die to a circuit board may be gradually slimmed from the semiconductor die to the circuit board. A dummy conductive layer may be disposed between the semiconductor die and the conductive pillar. A width of an opening for opening a pattern of the circuit board may range from about 50% to 90% of the width of the lower end of the conductive pillar. Accordingly, a mechanical stress is prevented from being transmitted from the conductive pillar to the semiconductor die, or is absorbed by the dummy conductive layer, and thus, preventing cracks of the semiconductor die and a dielectric layer having a low dielectric constant.