A method for forming a contact of a semiconductor device is disclosed. A first interlevel dielectric (ILD) layer is formed on a conductive region, e.g., an active region. The first ILD layer is etched to form a first contact hole therein to expose the conductive region. The first contact hole is filled with a porous layer having a high etch selectivity with respect to the first ILD layer to form a porous plug therein. Next, a second ILD layer is formed overlying the porous plug. The second ILD layer is etched to form a second contact hole therein to expose the porous plug. The porous plug in the first contact hole is removed. The first and second contact holes are filled with a conductive material to form a contact plug. During this contact formation process, the active region or the conductive region of the semiconductor substrate can be protected with the porous plug. Thus, the electrical characteristics degradation caused by dopant diffusion resulting from a thermal process during contact formation can be avoided.