METHOD OF FORMING ELEMENT ISOLATING FILM OF FLASH MEMORY ELEMENT

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flash memory element capable of suppressing an increase in film thickness of insulator after a subsequent insulating film deposition by preventing an oxide film from remaining on an upper side of conductive film for a floating gate through an etching step using etching ratio after depositing a nitride film in the form of liner on a trench prior to PSZ film deposition during a formation a element isolating film using PSZ-based materials, and improving a coupling ratio between the floating gate and a control gate by increasing a contact area between the floating gate and the insulating film. SOLUTION: The method for forming element isolating film of the flash memory element includes a step of forming a tunnel dielectric film, a conductive film and a first dielectric film in an active region, and a step of providing a substrate with a trench in an element isolating region. An element isolating region is formed by forming a dielectric film of side wall, a second dielectric film and a third dielectric film so that trench is filled with them. The first dielectric film is removed, although the first dielectric film remains in a state that upper parts of the third dielectric film and the side wall dielectric film are protruded, by etching upper parts of the third dielectric film and the second dielectric film. An etching process is implemented so that protrusions of the third dielectric film and the side wall dielectric film are removed to expose an upper side wall of the conductive film. COPYRIGHT: (C)2009,JPO&INPIT