Abstract: A method for forming a field oxide layer in a semiconductor device comprising the steps of: forming a pad oxide layer and a first resistant layer of oxidation, in turn, on a substrate; opening a field region by etching a portion of the said resistant layer of oxidation, whereby a part of the said pad oxide layer remains; forming the pad oxide layer into a nitric oxide layer; forming a second and a third resistant layer of oxidation, in turn, on a resultant structure; forming a spacer layer by applying anisotropic etching to the third resistant layer of oxidation; exposing a portion of the substrate by etching the second resistant layer of oxidation and the pad layer which is formed into the nitride layer; and forming the field oxide layer by oxidizing the substrate.

Abstract: A method of manufacturing a trench isolation comprising the steps of sequentially forming a first oxide layer a nitride layer and a first photoresist layer, forming a narrow trench and a wide trench, forming a first thermal oxide layer in the side and bottom face of trenches, forming a second oxide layer, depositing a first polysilicon oxide layer filling in the narrow trench by growing the first polysilicon layer growing into a second silicon layer, forming a third oxide layer, coating a second photoresist on the wide trench, and etching a third oxide layer. The present invention can provide a method of manufacturing a trench isolation which can prevent formation of voids in the narrow trench and the difference of height between narrow trench and wide trench, thereby preventing a conducting line short circuit and an increase of parasitic capacitance and a fall of the characteristic of the MOS transistor.