Transistor device and method of forming a field plate in an elongate active trench of a transistor device

In an embodiment, a method of forming a field plate in an elongate active trench of a transistor device is provided. The elongate active trench includes a first insulating material lining the elongate active trench and surrounding a gap and first conductive material filling the gap. The method includes selectively removing a first portion of the first insulating material using a first etch process, selectively removing a portion of the first conductive material using a second etch process, and forming a field plate in a lower portion of the elongate active trench and selectively removing a second portion of the first insulating material using a third etch process. The first etch process is carried out before the second etch process and the second etch process is carried out before the third etch process.