METHOD FOR FABRICATING SEMICONDUCTOR DEVICE TO PREVENT DEFECT CAUSED BY IMPURITY DENSITY VARIATION

摘要

PURPOSE: A method for fabricating a semiconductor device is provided to prevent a defect caused by an impurity density variation by minimizing a depth variation of a well in an active region and a field oxide layer of a semiconductor device having an STI(shallow trench isolation). CONSTITUTION: A pad nitride layer pattern overlapping a pad oxide layer pattern is formed on a semiconductor substrate(20). The semiconductor substrate exposed by the pad nitride layer pattern is etched to form a trench. An oxide layer(28) is formed on the inner wall of the trench. A field oxide layer(30) is formed on the resultant structure to fill the trench. The upper part of the field oxide layer is etched wherein the upper part of the pad nitride layer is etched together with the field oxide layer so that the upper part of the field oxide layer becomes higher than the upper part of the semiconductor substrate by a predetermined height. A predetermined thickness of the field oxide layer is etched wherein an Rp(projected range) according to a well impurity ion implantation becomes parallel with an Rp in consideration of a difference of an ion implantation depth among an oxide layer, a nitride layer and a semiconductor substrate. A well impurity ion implantation process is performed on the resultant structure to form a well impurity region(32) in parallel with the active region and the field oxide layer of the semiconductor substrate.