Method for producing a pillar-shaped semiconductor device

Abstract

A method for producing a pillar-shaped semiconductor device having a semiconductor pillar on a semiconductor substrate. A first material layer is formed surrounding the semiconductor pillar and the semiconductor substrate is etched using the first material layer as a mask to form a semiconductor-pillar base part under the semiconductor pillar that surrounds the semiconductor pillar in plan view. A second material layer is formed to cover an upper portion of the semiconductor-pillar base part and the first material layer. An oxidation-layer base part is formed at a lower portion of the semiconductor base part by oxidizing the semiconductor substrate and a lower portion of the semiconductor-pillar base part using the second material layer as an oxidation-resistant mask. The semiconductor pillar is within the oxidation-layer base part in plan view, and an upper surface of the oxidation-layer base part is lower than an upper surface of the semiconductor-pillar base part along a vertical direction.

1 . A method for producing a pillar-shaped semiconductor device including a semiconductor pillar, first and second impurity regions in contact with lower and upper portions of the semiconductor pillar, a gate insulating layer surrounding the semiconductor pillar between the first and second impurity regions in a vertical direction, and a gate conductor layer surrounding the gate insulating layer, the method comprising:
 forming the semiconductor pillar on a semiconductor substrate;   forming a first material layer surrounding the semiconductor pillar;   etching the semiconductor substrate using the first material layer as a mask to form a semiconductor-pillar base part under the semiconductor pillar, the semiconductor-pillar base part surrounding the semiconductor pillar in plan view;   forming a second material layer covering an upper portion of the semiconductor-pillar base part and the first material layer; and   forming an oxidation-layer base part at a lower portion of the semiconductor base part by oxidizing the semiconductor substrate and a lower portion of the semiconductor-pillar base part using the second material layer as an oxidation-resistant mask;   wherein the semiconductor pillar is positioned within the oxidation-layer base part in plan view, and an upper surface of the oxidation-layer base part is located lower than an upper surface of the semiconductor-pillar base part along a vertical direction.   
     
     
         2 . The method for producing a pillar-shaped semiconductor device according to  claim 1 , further comprising:
 forming a first mask material layer on the semiconductor substrate,   etching the semiconductor substrate through the first mask material layer serving as an etching mask to form the semiconductor pillar,   forming a second mask material layer surrounding a side surface of the semiconductor pillar, and   etching the semiconductor substrate through the first mask material layer and the second mask material layer serving as etching masks to form the semiconductor-pillar base part under the semiconductor pillar.   
     
     
         3 . The method for producing a pillar-shaped semiconductor device according to  claim 2 , further comprising:
 independently forming the first mask material layer and the second mask material layer as a single layer of a material providing a function of an etching mask and a function of an oxidation-resistant mask, or each independently formed as a plurality of layers including, in their outermost portion, the single layer,   wherein the first mask material layer and the second mask material layer constitute the oxidation-resistant mask.   
     
     
         4 . The method for producing a pillar-shaped semiconductor device according to  claim 2 , further comprises:
 forming a third-mask-material-layer by forming the oxidation-resistant mask so as to surround the semiconductor pillar with none of or at least one of the first mask material layer and the second mask material layer disposed between the oxidation-resistant mask and the semiconductor pillar, and so as to surround an upper side surface of the semiconductor-pillar base part.   
     
     
         5 . The method for producing a pillar-shaped semiconductor device according to  claim 4 , further comprising removing the first mask material layer or removing the second mask material layer, or removing both the first mask material layer and the second mask material layer. 
     
     
         6 . The method for producing a pillar-shaped semiconductor device according to  claim 4 , wherein forming the third-mask-material-layer includes forming the oxidation-resistant mask so as to surround the semiconductor pillar with the first mask material layer and the second mask material layer between the oxidation-resistant mask and the semiconductor pillar so as to surround the upper side surface of the semiconductor-pillar base part. 
     
     
         7 . The method for producing a pillar-shaped semiconductor device according to  claim 2 , wherein the second mask material layer is formed with a predetermined thickness so as to form the semiconductor-pillar base part having a predetermined width in plan view. 
     
     
         8 . The method for producing a pillar-shaped semiconductor device according to  claim 1 , further comprising:
 forming a plurality of the semiconductor pillars on and sharing the semiconductor-pillar base part, and   forming the second material layer so as to surround top portions and side surfaces of all the plurality of semiconductor pillars and a top portion of the semiconductor base part.   
     
     
         9 . The method for producing a pillar-shaped semiconductor device according to  claim 8 , further comprising:
 forming a plurality of first mask material layers on the semiconductor substrate;   etching the semiconductor substrate through the plurality of first mask material layers serving as etching masks to form the plurality of semiconductor pillars;   forming the second material layer so as to surround side surfaces of all the semiconductor pillars, and continuously extend between adjacent ones of the semiconductor pillars, and   etching the semiconductor substrate through the plurality of first mask material layers and the second mask material layer serving as etching masks, to form the semiconductor-pillar base part under and shared by the plurality of semiconductor pillars.   
     
     
         10 . The method for producing a pillar-shaped semiconductor device according to  claim 1 , further comprising:
 removing a portion of the second material layer, the portion having a band shape having a predetermined width in a height direction, to expose a side surface of the semiconductor pillar, and   using a remaining portion of the second material layer as an oxidation-resistant mask and oxidizing the exposed side surface of the semiconductor pillar to form an additional oxide insulating layer including, in its upper and lower regions, recessed portions within the semiconductor pillar.