In a method for fabricating an inter dielectric layer in semiconductor device, a primary liner HDP oxide layer is formed by supplying a high density plasma (HDP) deposition source to a bit line stack formed on a semiconductor substrate. A high density plasma (HDP) deposition source is supplied to the bit line stack to form a primary liner HDP oxide layer. The primary liner HDP oxide layer is etched to a predetermined depth to form a secondary liner HDP oxide layer. An interlayer dielectric layer is formed to fill the areas defined by the bit line stack where the secondary liner HDP oxide layer is located.