A method includes embedding a die in a molding material; forming a first dielectric layer over the molding material and the die; forming a conductive line over an upper surface of the first dielectric layer facing away from the die; and forming a second dielectric layer over the first dielectric layer and the conductive line. The method further includes forming a first trench opening extending through the first dielectric layer or the second dielectric layer, where a longitudinal axis of the first trench is parallel with a longitudinal axis of the conductive line, and where no electrically conductive feature is exposed at a bottom of the first trench opening; and filling the first trench opening with an electrically conductive material to form a first ground trench.