Nonvolatile semiconductor memory and method for fabricating the same
A nonvolatile semiconductor memory includes a first semiconductor layer; second semiconductor regions formed on the first semiconductor layer having device isolating regions extended in a column direction; a first interlayer insulator film formed above the first semiconductor layer; a lower conductive plug connected to the second semiconductor regions; a first interconnect extended in a row direction; a second interlayer insulator formed on the lower conductive plug and the first interlayer insulator film; an upper conductive plug; and a second interconnect formed on the second interlayer insulator contacting with the top of the upper conductive plug extended in the column direction.
1. A non-volatile semiconductor memory device, comprising:
a semiconductor substrate including a substrate surface;
a first interlayer insulating film formed on the substrate surface of the semiconductor substrate;
a second interlayer insulating film formed on the first interlayer insulating film;
a bit line formed on the second interlayer insulating film, the bit line extending to a first direction;
a first plug formed in the first interlayer insulating film, the first plug including:
a lower portion having a silicon material, the lower portion having a first bottom surface contacting to the semiconductor substrate, and
an upper portion located on the lower portion and having a metallic material, the upper portion having a first upper surface exposed from the first interlayer insulating film, the first upper surface having a first width along the first direction and a second width along a second direction perpendicular to the first direction;
a second plug formed in the second interlayer insulating film, including a second upper surface contacting to the bit line and a second bottom surface contacting to the first upper surface of the first plug, the second bottom surface having a send third width along the first direction and a forth width along the second direction, the second plug extending in a direction parallel to the first direction as a long-side direction; and
a plurality of gate electrodes of memory cell transistors formed above the substrate surface of the semiconductor substrate, each of the gate electrodes including a third upper surface;
wherein the third width is larger than the first width, the fourth width is smaller than the second width, and a height of an interface between the first and second interlayer insulating films is higher than a height of the third upper surface of the gate electrodes of the memory cell transistor relative to the substrate surface of the semiconductor substrate.
2. The device according to claim 1 , wherein the upper portion of the first plug includes an upper side surface contacting to the second plug.
3. The device according to claim 1 , further comprising a source line formed in the first interlayer insulating film, and a third plug formed between the source line and the semiconductor substrate.
4. The device according to claim 3 , wherein the source line includes a metallic material, and the third plug includes a silicon material.
5. The device according to claim 3 , wherein the source line extends to a second direction.
6. The device according to claim 3 , wherein the gate electrodes of memory cell transistors are disposed between the first and third plugs.
7. The device according to claim 6 , wherein each of the memory cell transistors includes a floating gate electrode, respectively.