Semiconductor memory device and method of manufacturing the same
According to one embodiment, a semiconductor memory device with memory cells each composed of a vertical transistor, comprises a silicon layer formed into a columnar shape on a silicon substrate, a gate insulating film part in which a tunnel insulating film, a charge storage layer, and a block insulating film are formed to surround the sidewall surface of the silicon layer, and a stacked structure part formed to surround the sidewall surface of the gate insulating film part and in which a plurality of interlayer insulating films and a plurality of control gate electrode layers are stacked alternately. The silicon layer, gate insulating film part, and control gate electrode layer constitute the vertical transistor. The charge storage layer has a region lower in trap level than a region facing the control gate electrode layer between the vertical transistors.
1. A method of manufacturing a semiconductor memory device, comprising:
forming, on a silicon substrate, a stacked structure part in which a plurality of interlayer insulating films and a plurality of control gate electrode layers are stacked one on top of another alternately;
forming a cell trench in the stacked structure part so as to attain the surface of the substrate;
forming a block insulating film, a charge storage layer, and a tunnel insulating film in that order along the sidewall of the cell trench;
forming a silicon layer in the cell trench so as to be buried in contact with the tunnel insulating film;
forming an element isolating trench in the gate electrode layer and interlayer insulating film in the vicinity of the cell trench;
isolating the charge storage layer in a direction perpendicular to the surface of the substrate by etching the interlayer insulating film, block insulating film, charge storage layer, and tunnel insulating film with the control gate electrode as a mask after the formation of the element isolating trench; and
forming a new interlayer insulating film in a part where the interlayer insulating film, block insulating film, charge storage layer, and tunnel insulating film have been etched so as to be buried in the part.
2. The method according to claim 1 , wherein the cell trench comprises a plurality of cell trenches, the cell trenches arranged in rows and columns and the element isolating is formed between neighboring ones of the columns.
3. The method according to claim 1 , wherein the cell trench and element isolating trench are formed by RIE and the interlayer insulating film, block insulating film, charge storage layer, and tunnel insulating film are etched by wet etching.
4. A method of manufacturing a semiconductor memory device, comprising:
forming a stacked structure part in which a plurality of first films and a plurality of second films are alternately stacked above a silicon substrate, the first films having an etching selectivity to the second films;
forming a plurality of openings, each opening being circular or elliptical in a plan view, in the stacked structure part in a direction substantially perpendicular to a surface of the silicon substrate;
forming a gate insulating film part including at least a charge storage layer along a sidewall of each of the plurality of openings;
forming a semiconductor layer in contact with the gate insulating film part in each of the plurality of openings;
forming an isolating trench through the first films and the second films in vicinity of the openings; and
isolating the charge storage layer in the direction substantially perpendicular to the surface of the silicon substrate, by etching the plurality of first films of the stacked structure part and at least the charge storage layer in the gate insulating part through the isolating trench.
5. The method according to claim 4 , wherein the plurality of openings are arranged in rows and columns and the isolating trench is formed between neighboring ones of the columns.
6. The method according to claim 4 , wherein the plurality of openings and the isolating trench are formed by RIE and the plurality of first films and the charge storage layer are etched by wet etching.
7. A method of manufacturing a semiconductor memory device, comprising:
forming an object to be processed, which comprises a stacked structure part in which a plurality of control gate electrode layers and a plurality of inter-gate layers are alternately stacked above a silicon substrate, a columnar member formed in the stacked structure part in a direction substantially perpendicular to a surface of the silicon substrate, the member including a semiconductor layer, to be accompanied by a gate insulating film part formed between the semiconductor layer and the stacked structure part, the gate insulating film part including at least a charge storage layer and being formed along a sidewall of the semiconductor layer;
after the forming the object, forming an isolating trench through the stacked structure part in vicinity of the columnar member;
removing, through the isolating trench, each of the inter-gate layers between the control gate electrode layers neighboring in the direction substantially perpendicular to the surface of the silicon substrate; and
isolating the charge storage layer in the direction substantially perpendicular to the surface of the silicon substrate, by etching the charge storage layer positioned at a same height as the removed inter-gate layers through the isolating trench.
8. The method according to claim 7 , wherein a plurality of columnar members, each being the columnar member, are arranged in rows and columns and the isolating trench is formed between neighboring ones of the columns.
9. The method according to claim 7 , wherein the isolating trench is formed by RIE.
10. The method according to claim 9 , wherein the inter-gate layers are removed by wet etching.
11. The method according to claim 9 , wherein the charge storage layer is etched by wet etching.