Data retention of EEPROM cell with shallow trench isolation using thicker liner oxide

摘要

A shallow trench isolation structure and a method for forming the same for use with non-volatile memory devices is provided so as to maintain sufficient data retention thereof. An epitaxial layer is formed on a top surface of a semiconductor substrate. A barrier oxide layer is formed on a top surface of the epitaxial layer. A nitride layer is deposited on a top surface of the barrier oxide layer. Trenches are formed through the epitaxial layer and the barrier oxide layer to a depth greater than 4000 ANGSTROM below the surface of the epitaxial layer so as to create isolation regions in order to electrically isolate active regions in the epitaxial layer. A liner oxide is formed on sidewalls and bottom of the trenches to a thickness between 750 ANGSTROM to 1500 ANGSTROM . As a result, leakage current in the sidewalls are prevented due to less thinning of the liner oxide layer by subsequent fabrication process steps.