Semiconductor device and method for fabricating the same

A semiconductor device, comprising:

• a gate structure arranged on a substrate, wherein the gate structure comprises a gate insulating film disposed on the substrate, a first gate conductive film disposed on the gate insulating film, a second gate conductive film disposed on the first gate conductive film, and a gate mask film disposed on the second gate conductive film;
• a plurality of word lines arranged apart from the gate structure;
• two porous spacers arranged on and in contact with two sides of the gate structure, such that the porous spacers are in contact with sidewalls of the gate mask film, sidewalls of the second gate conductive film, sidewalls of the first gate conductive film, and sidewalls of the gate insulating film;
• a first insulating layer arranged on the substrate laterally surrounding the gate structure and the porous spacers;
• a second insulating layer arranged over the first insulating layer, and
• two spacers attached to outer sides of the two porous spacers, wherein the spacers are made of a same material of the porous spacers, such that the spacers forms two outer porous spacers respectively and each of the spacers is constructed to have a skeleton and a plurality of empty spaces disposed and distributed among the skeleton;
• wherein a top surface of the gate structure, top surfaces of the plurality of word lines and a top surface of the second insulating layer are level with each other,
• wherein each of the porous spacers is constructed to have a skeleton and a plurality of empty spaces disposed and distributed among the skeleton;
• and
• wherein a porosity of the porous spacers is between about 25% and about 100%.