US Patent 11908702 Gate structures in semiconductor devices

A semiconductor device with different configurations of gate structures and a method of fabricating the same are disclosed. The method includes forming a fin structure on a substrate, forming a gate opening on the fin structure, forming a metallic oxide layer within the gate opening, forming a first dielectric layer on the metallic oxide layer, forming a second dielectric layer on the first dielectric layer, forming a work function metal (WFM) layer on the second dielectric layer, and forming a gate metal fill layer on the WFM layer. The forming the first dielectric layer includes depositing an oxide material with an oxygen areal density less than an oxygen areal density of the metallic oxide layer.