METHOD OF FORMING DUAL FIELD ISOLATION STRUCTURES

摘要

A method of providing thick and thin oxide structures (142, 146) reduces step changes between a core region (108) and a peripheral region (109) on an integrated circuit (112). Thin LOCOS structures (146) are provided in a core region (108) and a peripheral region (109) on an integrated circuit (112). Thin LOCOS structures (146, 148) are provided in a core region (108) of a flash memory device, and thick LOCOS structures (142, 144) are provided in a peripheral region (109) of the flash memory device. The device and process are not as susceptible to "race track" problems, "oxide" bump problems, and "stringer" problems. The process utilizes two separate nitride or hard mask layers (118, 160).