According to an embodiment, a chip package is provided, which includes: a substrate having a first surface and a second surface; a device region formed in the substrate; a passivation layer formed overlying the first surface of the substrate; at least a polymer planarization layer formed overlying the passivation layer; a package substrate disposed overlying the first surface of the substrate; and a spacer layer disposed between the package substrate and the passivation layer, wherein the spacer layer and the package substrate surround a cavity overlying the substrate, wherein the polymer planar layer does not extends to an outer edge of the spacer layer.