Method for forming flowable dielectric layer in semiconductor device

The method for forming a flowable dielectric layer without micro-voids therein in a semiconductor device is employed to utilize a ultra-violet (UV) bake process. The method includes steps of: forming a plurality of patterns on a semiconductor substrate, wherein narrow and deep gaps are formed therebetween; forming a flowable dielectric layer so as to fill the gaps between the patterns; carrying out a baking process for densifying the flowable dielectric layer from a bottom face thereof; forming a plurality of contact holes by selectively etching the flowable dielectric layer; carrying out a pre-cleaning process in order to remove native oxide and impurity substances on the contact holes; and forming a plurality of contact plugs by filling a conductive material into the contact holes.