METHOD FOR FORMING ISOLATION LAYER OF SEMICONDUCTOR DEVICE

摘要

A method for forming an isolation layer in a semiconductor device is provided to form an isolation layer without voids in a trench by using an undoped polysilicon layer with excellent coverage and by transforming the used undoped polysilicon layer into an oxide layer by an annealing process. On a semiconductor substrate(10) including an active region and an isolation region, a hard mask layer exposing the isolation region is formed. The exposed part of the substrate is etched by using the hard mask layer to form trenches(30) with different widths. A sidewall oxide layer(40), a liner nitride layer and a liner oxide layer are sequentially formed on the surface of the trenches. A first oxide layer(50) is formed on the resultant structure in a maximum range that doesn't completely fill the trench of the smallest width among the trenches. An undoped polysilicon layer is formed on the first oxide layer to completely fill the trench of the smallest width. The undoped polysilicon layer is oxidized to form a second oxide layer(60). A third oxide layer(70) is formed on the second oxide layer to completely fill the trench of the greatest width. A CMP process is performed on the first, second and third oxide layers until the hard mask layer is exposed. The hard mask layer is eliminated.