Disclosed is a structure and method for forming a structure including a SiCOH layer having increased mechanical strength. The structure includes a substrate having a layer of dielectric or conductive material, a layer of oxide on the layer of dielectric or conductive material, the oxide layer having essentially no carbon, a graded transition layer on the oxide layer, the graded transition layer having essentially no carbon at the interface with the oxide layer and gradually increasing carbon towards a porous SiCOH layer, and a porous SiCOH (pSiCOH) layer on the graded transition layer, the porous pSiCOH layer having an homogeneous composition throughout the layer. The method includes a process wherein in the graded transition layer, there are no peaks in the carbon concentration and no dips in the oxygen concentration.