Nonvolatile memories and methods of fabrication

Abstract

In a nonvolatile memory, substrate isolation regions () are formed in a semiconductor substrate (). The substrate isolation regions are dielectric regions protruding above the substrate. Then select gate lines () are formed. Then a floating gate layer () is deposited. The floating gate layer is etched until the substrate isolation regions are exposed and the floating layer is removed from over at least a portion of the select gate lines. A dielectric () is formed over the floating gate layer, and a control gate layer () is deposited. The control gate layer protrudes upward over each select gate line. These protrusions are exploited to define the control gates independently of photolithographic alignment. The floating gates are then defined independently of any photolithographic alignment other than the alignment involved in patterning the substrate isolation regions and the select gate lines. In another aspect, a nonvolatile memory cell has a conductive floating gate (). A dielectric layer () overlying the floating gate has a continuous feature that overlies the floating gate and also overlies the select gate (). The control gate () overlies the continuous feature of the dielectric layer and also overlies the floating gate but not the select gate. In another aspect, substrate isolation regions () are formed in a semiconductor substrate. Select gate lines cross over the substrate isolation regions. Each select gate line has a planar top surface, but its bottom surface goes up and down over the substrate isolation regions. Other features are also provided.