A driver circuit for a three-dimensional (3D) memory device has a field management structure electrically coupled to a gate conductor. The field management structure causes an electric field peak in a vertical channel of the 3D memory device when a voltage differential exists between the source conductor and the drain conductor and the gate conductor is not biased. The electrical field peak can adjust the electrical response of the driver circuit, enabling the circuit to have a higher breakdown threshold voltage and improved drive current. Thus, the driver circuit can enable a scalable vertical string driver that is above the memory array instead of under the memory array circuitry.

A memory device includes a semiconductor substrate, a first continuous floating gate structure, a dielectric layer, and a control gate electrode. The semiconductor substrate has a first active region. The first continuous floating gate structure is over the first active region of the semiconductor substrate, wherein the first continuous floating gate structure has first and second inner sidewalls facing each other. The dielectric layer has a first portion extending along the first inner sidewall of the first continuous floating gate structure and a second portion extending along the second inner sidewall of the first continuous floating gate structure. The control gate electrode is over the dielectric layer. The control gate electrode is in contact with the first and second portions of the dielectric layer.