A semiconductor package with reduced warpage problem is provided, including: a circuit board, having opposing first and second surfaces; a semiconductor chip, formed over a center portion of the first surface of the circuit board, having a first cross sectional dimension; a spacer, formed over a center portion of the semiconductor chip, having a second cross sectional dimension less than that of the first cross sectional dimension; an encapsulant layer, formed over the circuit board, covering the semiconductor chip and surrounding the spacer; a heat spreading layer, formed over the encapsulant layer and the spacer; and a plurality of solder balls, formed over the second surface of the circuit board, wherein a ratio between the first cross sectional dimension and the second cross sectional dimension is about 1:2-1:6.