| 摘要 |
In a memory cell ( 110 ) having multiple floating gates ( 160 ), the select gate ( 140 ) is formed before the floating gates. In some embodiments, the memory cell also has control gates ( 170 ) formed after the select gate. Substrate isolation regions ( 220 ) are formed in a semiconductor substrate ( 120 ). The substrate isolation regions protrude above the substrate. Then select gate lines ( 140 ) are formed. Then a floating gate layer ( 160 ) is deposited. The floating gate layer is etched until the substrate isolation regions are exposed. A dielectric ( 164 ) is formed over the floating gate layer, and a control gate layer ( 170 ) is deposited. The control gate layer protrudes upward over each select gate line. These the control gates and the floating gates are defined independently of photolithographic alignment. In another aspect, a nonvolatile memory cell has at least two conductive floating gates ( 160 ). A dielectric layer ( 164 ) overlying the floating gate has a continuous feature that overlies the floating gate and also overlays a sidewall of the select gate ( 140 ). Each control gate ( 160 ) overlies the continuous feature of the dielectric layer and also overlies the floating gate. In another aspect, substrate isolation regions ( 220 ) 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.
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