METHOD OF FORMING AN ISOLATION IN A SEMICONDUCTOR DEVICE

A method for forming an isolation layer in a semiconductor device is provided to prevent formation of voids by burying an isolation layer while using a polysilicon layer with an excellent filling characteristic. A part of a semiconductor substrate(100) is etched to form a trench. After a first oxide layer(110) is formed on the resultant structure, a polysilicon layer(112) is formed on the resultant structure to fill the trench. The polysilicon layer can be formed by depositing a doped polysilicon layer in a furnace. The polysilicon layer is etched to make the surface of the polysilicon layer lower than the surface of the semiconductor substrate. A second oxide layer(114) made of an HDP(high density plasma) oxide layer is formed on the resultant structure to fill the trench so that an isolation layer(116) is formed.