a method for isolation region fabrication for replacement gate integrated circuit processing includes forming a plurality of dummy gates on a substrate ; forming a block mask over the plurality of dummy gates , such that the block mask selectively exposes a dummy gate of the plurality of dummy gates ; removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate ; filling the isolation region recess with an insulating material to form an isolation region ; removing the block mask to expose a remaining plurality of dummy gates ; and performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices , wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region .