Nonvolatile semiconductor memory and process of producing the same
A nonvolatile semiconductor memory of an aspect of the present invention comprises a semiconductor substrate, a pillar-shaped semiconductor layer extending in the vertical direction with respect to the surface of the semiconductor substrate, a plurality of memory cells arranged in the vertical direction on the side surface of the semiconductor layer and having a charge storage layer and a control gate electrode, a first select gate transistor arranged on the semiconductor layer at an end of the memory cells on the side of the semiconductor substrate, and a second select gate transistor arranged on the semiconductor layer on the other end of the memory cells opposite to the side of the semiconductor substrate, wherein the first select gate transistor includes a diffusion layer in the semiconductor substrate and is electrically connected to the pillar-shaped semiconductor layer by way of the diffusion layer that serves as the drain region.
1. A method of manufacturing a nonvolatile semiconductor memory comprising steps of:
forming a gate electrode of a first select gate transistor on a gate insulating film deposited on a surface of a semiconductor substrate;
forming a diffusion layer to serve as source and drain regions of the first select gate transistor by using the gate electrode as a mask;
alternately depositing interlayer insulating films and control gate electrode material of memory cells on the gate electrode and the semiconductor substrate;
forming gate electrode material of a second select gate transistor on an interlayer insulating film positioned at an end opposite to the semiconductor substrate;
sequentially etching the gate electrode material of the second select gate transistor, the control gate electrode material and the interlayer insulating films and thereby exposing a top surface of the diffusion layer to serve as the drain region of the first select gate transistor;
forming a first insulating film on a side surface of the control gate electrode material and the gate electrode material of the second select gate transistor;
forming a charge storage layer on a side surface of the first insulating film;
removing portions of the first insulating film and the charge storage layer deposited on the side surface of a gate electrode of the second select gate transistor;
forming a second insulating film on the side surface of the charge storage layer and the gate electrode of the second select gate transistor; and
forming a pillar-shaped semiconductor layer on a side surface of the second insulating film.
2. The method of the manufacturing the nonvolatile semiconductor memory according to claim 1 , further comprising steps of:
forming a source line in such a manner as to be connected to the diffusion layer that serves as the source region of the first select gate transistor after the step of forming the diffusion layer to serve as the source and drain regions of the first select gate transistor; and
forming the interlayer insulating film on the top surface of the source line and on the gate electrode of the first select gate transistor.
3. The method of the manufacturing the nonvolatile semiconductor memory according to claim 1 , further comprising steps of:
forming a gate electrode of a peripheral transistor on a gate insulating film deposited on the surface of the semiconductor substrate at a same timing as the step of forming the gate electrode of the first select gate transistor; and
forming a diffusion layer to serve as source and drain regions of the peripheral transistor at a same timing as the step of forming the diffusion layer to serve as the source and drain regions of the first select gate transistor.