Patent ID: 7791133

Claim:
A semiconductor device, comprising: a semiconductor substrate; a vertically extending portion of semiconductor disposed above the semiconductor substrate, the vertically extending portion of semiconductor having top and bottom portions and a side surface; a first diffusion region disposed near the bottom portion of the vertically extending portion of semiconductor and positioned in the semiconductor substrate, the first diffusion region including a first diffusion portion extending along a horizontal direction along a surface of the semiconductor substrate and a second diffusion portion extending from the first diffusion portion along a vertical direction along the side surface of the vertically extending portion of semiconductor; a second diffusion region disposed near the top portion of the vertically extending portion of semiconductor; a gate insulating film extending along the side surface of the vertically extending portion of semiconductor; a gate electrode disposed on the gate insulating film, the gate electrode opposed to the side surface, the level of a top portion of the gate electrode being nearly equal to or lower than the level of a bottom portion of the second diffusion region, and the level of a bottom portion of the gate electrode being nearly equal to or higher than the level of a top portion of the first diffusion region; and an insulating layer positioned under the gate electrode and over the surface of the semiconductor substrate, wherein the second diffusion portion of the first diffusion layer has an upper surface that is at a lower level than a top surface of the insulating layer and is at a higher level than a bottom surface of the insulating layer.