Method of manufacturing trench isolation

Claim 1

A method of manufacturing a trench isolation on a semiconductor substrate, comprising the steps of: sequentially forming a first oxide layer, a nitride layer and a first photoresist layer on the substrate, forming narrow trenches and wide trenches to have a depth, forming a first thermal oxide layer on the side and bottom face of trenches, forming a second oxide layer to have a depth on the entire structure, depositing a first polysilicon layer to have a depth on the second oxide layer, filling in the trenches by oxidizing the first polysilicon layer to form a second thermal oxide layer, forming a second polysilicon layer on the second thermal oxide to have a depth, forming a third oxide layer to have a thickness extending from the nitride layer to the second thermal oxide layer, on the entire resulting structure, coating a second photoresist on the wide trenches, etching the third oxide layer by using the resulting exposed portion of the second photoresist as etch barrier, eliminating the second polysilicon layer and the second photoresist, flatly coating a third photoresist or BPSG on the entire structure, etching the third photoresist or BPSG, etching the third oxide layer until the second polysilicon layer and nitride layer are exposed, and eliminating the second polysilicon layer of the wide trenches and the nitride layer to form trenches including the first thermal oxide layer and the second thermal oxide layer.

Claim 2

A method of manufacturing a trench isolation on a semiconductor substrate, comprising the steps of: sequentially forming a first oxide layer, a nitride layer and a first photoresist layer on the substrate, forming narrow trenches and wide trenches to have a depth, forming a first thermal oxide layer on the side and bottom face of trenches, forming a second oxide layer to have a depth on the entire structure, depositing a first polysilicon layer to have a depth on the second oxide layer, filling in the trenches by oxidizing the first polysilicon layer to form a second thermal oxide layer, forming a second polysilicon layer on the second thermal oxide to have a depth, forming a third oxide layer to have a thickness extending from the nitride layer to the second thermal oxide layer, on the entire resulting structure, coating a second photoresist on the wide trenches, etching the third oxide layer by using the resulting exposed portion of the second photoresist as etch barrier, eliminating the second polysilicon layer and the second photoresist, flatly coating a third photoresist or BPSG on the entire structure, etching the third photoresist or BPSG, etching the third oxide layer until the second polysilicon layer and nitride layer are exposed, and eliminating the second polysilicon layer of the wide trenches and the nitride layer to form trenches including the first thermal oxide layer and the second thermal oxide layer.