Self-aligned charge storage region formation for semiconductor device
View Patent ↗Devices and methods for forming self-aligned charge storage regions are disclosed. In one embodiment, a method for manufacturing a semiconductor device comprises forming a layer of a nitride film stacked between two oxide films on a semiconductor substrate, and forming a gate electrode on the layer of the nitride film stacked between the two oxide films. In addition, the method comprises removing side portions of the nitride film such that a central portion of the nitride film below a center portion of the gate electrode remains, oxidizing the central portion of the nitride film, and forming charge storage layers in the side portions of the nitride film, where the charge storage layers are separated by the central portion of the nitride film.
1. A method for manufacturing a semiconductor device, the method comprising:
forming a layer of a nitride film stacked between two oxide films on a semiconductor substrate;
forming a gate electrode on the layer of the nitride film stacked between the two oxide films;
removing side portions of the nitride film such that a central portion of the nitride film below a center portion of the gate electrode remains;
oxidizing the central portion of the nitride film; and
forming charge storage layers in the side portions of the nitride film,
wherein the charge storage layers are separated by the central portion of the nitride film.
2. The method of claim 1 , wherein the two oxide films comprise:
a tunnel oxide film formed on the semiconductor substrate; and
a top oxide film formed on the nitride film.
3. The method of claim 2 , wherein the forming the gate electrode comprises:
forming a polysilicon layer on the layer of nitride film stacked between the two oxide films;
forming a mask layer on the polysilicon layer; and
etching the polysilicon layer, the top oxide film, and the nitride film using the mask layer to form the gate electrode.
4. The method of claim 2 , wherein the forming the gate electrode comprises:
forming a polysilicon layer on the layer of nitride film stacked between the two oxide films;
forming a photoresist on the polysilicon layer; and
etching the polysilicon layer, the top oxide film, and the nitride film using the photoresist to form the gate electrode.
5. The method of claim 1 , wherein the oxidizing the central portion of the nitride film comprises oxidizing the central portion of the nitride film completely.
6. The method of claim 1 , wherein the oxidizing the central portion of the nitride film comprises oxidizing end portions of the central portion of the nitride film.
7. The method of claim 1 , wherein the removing side portions of the nitride film is performed by using an isotropic etching.
8. The method of claim 1 , wherein the oxidizing the central portion of the nitride film is performed by using a plasma oxidation.
9. The method of claim 1 , wherein the oxidizing the central portion of the nitride film is performed by using radical oxidation.
10. The method of claim 1 , wherein the forming the charge storage layers comprises:
forming the charge storage layers along the side portions of the nitride film and along side surfaces of the gate electrode; and
oxidizing the charge storage layers formed along the side surfaces of the gate electrode.
11. The method of claim 1 , wherein the forming the charge storage layers comprises:
forming the charge storage layers along the side portions of the nitride film and along side surfaces of the gate electrode; and
forming sidewall layers on side surfaces of the charge storage layers so as to cover the charge storage layers formed on the side surfaces of the gate electrode.
12. The method of claim 11 , wherein side surfaces of the charge storage layers on the side surfaces of the gate electrode are not oxidized.
13. The method of claim 1 , the method further comprising forming a source region and a drain region in the semiconductor substrate by using the gate electrode as a mask.