Semiconductor device and method of forming same

A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate trench crossing an active region, and a gate structure in the gate trench. The gate structure includes a gate dielectric layer disposed on an inner wall of the gate trench, a gate electrode disposed on the gate electric layer and partially filling the gate trench, a gate capping insulating layer disposed on the gate electrode, and a gap-fill insulating layer disposed in the gate trench and disposed on the gate capping insulating layer. The gate capping insulating layer includes a material formed by oxidizing a portion of the gate electrode, nitriding the portion of the gate electrode, or oxidizing and nitriding the portion of the gate electrode. 提供一种半导体器件及形成其的方法。该半导体器件包括交叉有源区域的栅极沟槽以及在栅极沟槽中的栅极结构。栅极结构包括：设置在栅极沟槽的内壁上的栅极电介质层、设置在栅极电介质层上并部分地填充栅极沟槽的栅电极、设置在栅电极上的栅极盖绝缘层、以及设置在栅极沟槽中并设置在栅极盖绝缘层上的间隙填充绝缘层。栅极盖绝缘层包括通过氧化栅电极的一部分、氮化栅电极的一部分、或者氧化和氮化栅电极的一部分而形成的材料。