Patent ID: 7550394

Claim:
A method of forming a shallow trench device isolation structure, in which a device isolation trench in a silicon substrate is filled with an insulation film, said method comprising a step of forming said device isolation trench in said silicon substrate by a dry etching process of said silicon substrate, and filling the insulation film in the device isolation trench, wherein said dry etching process is conducted by an etching gas containing at least one gas specie selected from the group consisting of: HBr, HCl, Cl 2 , Br 2 and HI, said dry etching process comprising: a first step conducted at a first temperature; and a second step conducted at a second temperature, wherein said second temperature is lower than said first temperature, said first step of said dry etching process forming a first trench part in said silicon substrate in correspondence to said device isolation trench, said second step of said dry etching process forming a second, tapered trench part at a bottom of said first trench part, said second trench part forming a shallower angle than said first trench part forming a shallower angle than said first trench part with regard to a surface of said silicon substrate and having a tapered shape, said second trench part having a second width at a bottom thereof such that said second width is smaller than a first width at said bottom of said first trench part.