METHOD OF FORMING A ISOLATION LAYER IN SEMICONDUCTOR DEVICE

PURPOSE: A method of forming an isolation layer in a semiconductor device is provided to form an element isolation film without a defective by forming an low element isolation film and forming it to be final height again. CONSTITUTION: In a device, a trench is formed in an element isolation region of a semiconductor substrate(102). A tunnel insulating film(104), a first conductive film(106), and a first hard mask film are formed in an active area of the semiconductor substrate. The trench is filled with the first insulating film(112), and the first insulating film is left on the trench through a first planarization process. A second conductive film(114) and a second hard mask film(116) are formed on the first conductive film and the first insulating film. The second insulating film(118) is formed between the second hard mask film and the second conductive film.