Patent ID: 8237199

Claim:
A method of forming a cell array of a semiconductor memory device, the method comprising: forming an active region that is constituted by a first region of semiconductor material having a substantially planar top surface, a second region of semiconductor material having a substantially planar top surface located at a level different from that of the top surface of the first region, and a transition region of semiconductor material having a surface that is inclined relative to each of the top surfaces of the first and second regions and wherein the transition region is interposed between and connects the second region and the first region; forming a plurality of word lines extending longitudinally across the first region; and forming a selection line extending longitudinally across the active region, wherein at least a portion of the selection line is located over the top surface of the transition region and the selection line has opposite sidewalls, one of the sidewalls extending upright on the surface of one of said regions that constitutes the active region, the other of the sidewalls extending upright on the surface of another of said regions that constitutes the active region, and the sidewalls having different vertical dimensions such that one of the sidewalls is taller than the other.