Semiconductor device and method of forming the same

Abstract

A method of forming a semiconductor device includes etching through a metal gate structure to form a trench between a first and a second active region; depositing a barrier layer in the trench, the barrier layer conforms to and partially fills the trench; depositing a sacrificial layer over the barrier layer to fully fill the trench; planarizing top surfaces of the barrier layer and the sacrificial layer to form a gate isolation feature having the barrier layer and the sacrificial layer; thinning down the substrate and the gate isolation feature from a backside to form an opening in the barrier layer; removing the sacrificial layer through the opening to form a modified gate isolation feature, the modified gate isolation feature having an air gap between portions of the barrier layer; and forming a capping layer on the backside of the modified gate isolation feature to seal the air gap.

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