Patent ID: 7863153

Claim:
A method for manufacturing a field oxide in an integrated circuit, the method comprising the step of: forming (i) a first portion of the field oxide with a first field oxide profile and (ii) a second portion of the field oxide with a second field oxide profile during a field oxide oxidation process; wherein forming the first and second portions of the field oxide comprises: forming a pad oxide layer over a silicon substrate; forming additional pad oxide over a portion of the pad oxide layer where the second portion of the field oxide is being formed; forming a layer of silicon nitride over the pad oxide layer and over the additional pad oxide; applying a mask and etch procedure to the silicon nitride layer to form a silicon nitride mask over the pad oxide layer and over the additional pad oxide; exposing portions of the pad oxide layer to the oxidation process to create the first portion of the field oxide; and exposing portions of the additional pad oxide to the oxidation process to create the second portion of the field oxide; wherein the first field oxide profile comprises an abrupt bird's beak profile; and wherein the second field oxide profile comprises a graded bird's beak profile.