Provided is a integrated circuit device and a method for fabricating the same. The integrated circuit device includes a semiconductor substrate having a dielectric layer disposed over the semiconductor substrate and a passive element disposed over the dielectric layer. The integrated circuit further includes an isolation matrix structure, underlying the passive element, wherein the isolation matrix structure includes a plurality of trench regions each being formed through the dielectric layer and extending into the semiconductor substrate, the plurality of trench regions further including an insulating material and a void area.