Method for manufacturing semiconductor device having 4F2 transistor
Provided is a method for manufacturing a semiconductor device having a 4F2 transistor. In the method, a gate stack is formed on a semiconductor substrate. A first interlayer dielectric including a contact hole which includes a first region and second regions Spacer layers are formed on both sides of the gate stack and a portion of the second region. Landing plugs are formed on the contact hole, a portion of the semiconductor substrate exposed by a thickness of the spacer layer, and a lateral side of the trench. A second interlayer dielectric is formed to separate the landing plug. The bit line contact plug is connected to a first portion of the landing plug that extends to the lateral side of the trench. The bit line stack is connected to the bit line contact plug. The storage node contact plug is connected to the first portion and a second portion of the landing plug located at a corresponding position in a diagonal direction.
1. A method for manufacturing a semiconductor device having a 4F2 transistor, the method comprising:
forming a device isolation layer defining an active region on a semiconductor substrate, wherein the active region is disposed in a shape of a vertical stripe;
forming gate stacks on the active region of the semiconductor substrate;
forming a first interlayer dielectric to fill between adjacent gate stacks;
forming a contact hole through the first interlayer dielectric, the contact hole including a first region exposing portions of two facing sides of the adjacent gate stacks, and two second regions extending outwardly from the first region in opposite directions to expand the exposed portions of the two facing sides of the adjacent gate stacks from two diagonally opposed corners of the first region;
forming spacer layers on the exposed portions of the two facing sides of the adjacent gate stacks, including filling the two second regions of the contact hole;
forming a trench inside the semiconductor substrate by performing an etching process using the spacer layers as an etch mask and then removing the spacer layers;
forming first and second landing plugs on the two facing sides of the adjacent gate stacks, respectively, exposed by the first region and the two second regions of the contact hole, on a portion of the semiconductor substrate exposed by removing the spacer layers, and on a lateral side of the trench, wherein the first and second landing plugs partially fill the contact hole while exposing a bottom surface of the trench;
filling the trench with a second interlayer dielectric to separate the first and second landing plugs;
forming a bit line contact plug connected to the first landing plug and a bit line stack connected to the bit line contact plug; and
forming a storage node contact plug connected to the second landing plug and a storage node electrode connected to the storage node contact plug.
2. The method of claim 1 , wherein the forming of the gate stacks comprises:
forming recess trenches inside the active region of the semiconductor substrate;
forming the gate stacks overlapping the recess trenches; and
forming an impurity region inside the semiconductor substrate by performing a junction ion implantation process on the semiconductor substrate.
3. The method of claim 2 , wherein each of the recess trenches exposes the semiconductor substrate by a width of approximately 1 F in an x-axis direction and by a width of approximately 0.5 F in a y-axis direction of the semiconductor substrate, where F is a minimum feature size.
4. The method of claim 2 , wherein a target of the ion implantation process is set such that when the recess trenches are formed to a depth of approximately 1200 to 2000 Å, the bottom of the impurity region is located at approximately ⅔ to ¾ of a depth of the recess trenches.
5. The method of claim 1 , wherein the second regions of the contact hole formed in the first interlayer dielectric are formed in a rectangular shape of approximately 0.5 F ×0.25, where F is a minimum feature size.
6. The method of claim 1 , wherein the spacer layer comprises a nitride layer.
7. The method of claim 1 , wherein the trench is formed to have a depth of approximately 600 to 1000 Å from a surface of the semiconductor substrate.
8. The method of claim 1 , wherein one of the first interlayer dielectric and the second interlayer dielectric comprises one of a spin-on-dielectric (SOD) and a boron phosphorous silicate glass (BPSG) layer.
9. The method of claim 1 , wherein the forming of the first and second landing plugs comprises:
depositing a conductive layer on the semiconductor substrate after the removing of the spacer layers; and
forming the first and second landing plugs on the two facing sides of the adjacent gate stacks, respectively, on a portion of the semiconductor substrate exposed by the thickness of the spacer layer, and on the lateral side of the trench by removing the conductive layer on the bottom surface of the trench.
10. The method of claim 9 , wherein the conductive layer comprises a polysilicon layer deposited to have a thickness of approximately 50 to 300 Å.
11. The method of claim 9 , wherein the conductive layer is removed using one of an etch back process and a chemical mechanical polishing (CMP) process.
12. The method of claim 1 , wherein the bit line contact plug and the storage node contact plug are formed on positions that are separated by approximately 0.5 F from the device isolation layer adjacent to the gate stacks, respectively.
13. The method of claim 1 , wherein the bit line contact plug and the storage node contact plug are arranged at positions separated from each other in a diagonal direction.