US Patent 8742492 Device with a vertical gate structure

A device includes a wafer substrate, a conical frustum structure formed in the wafer substrate, and a gate all-around (GAA) structure circumscribing the middle portion of the conical frustum structure. The conical frustum structure includes a drain formed at a bottom portion of the conical frustum, a source formed at a top portion of the vertical conical frustum, and a channel formed at a middle portion of the conical frustum connecting the source and the drain. The GAA structure overlaps with the source at one side of the GAA structure, crosses over the channel, and overlaps with the drain at another side of the GAA structure.