Disclosed is a method for fabricating a semiconductor device with an improved tolerance to a wet cleaning process. For a contact formation such as a gate structure, a bit line or a metal wire, a spin on glass (SOG) layer employed as an inter-layer insulation layer becomes tolerant to the wet cleaning process by allowing even a bottom part of the SOG layer to be densified during a curing process. The SOG layer is subjected to the curing process after a maximum densification thickness of the SOG layer is obtained through a partial removal of the initially formed SOG layer or through a multiple SOG layer each with the maximum densification thickness. After the SOG layer is cured, a self-aligned contact etching process is performed by using a photoresist pattern singly or together with a hard mask.