Local word line driver device, memory device, and fabrication method are provided. A local word line driver device includes a substrate and an array of transistor structures formed on the substrate. The transistor structures are configured in rows and columns. The substrate includes a plurality of first field regions each between adjacent rows of the transistor structures, and a plurality of second field regions each between adjacent columns of the transistor structures. A deep trench isolation structure is formed in at least one field region of: the plurality of first field regions or the plurality of second field regions, of the substrate.