Semiconductor device and method of manufacturing the same
Provided herein is a semiconductor device and a method of manufacturing the same. The semiconductor device has improved erase characteristics by using a select gate enclosing a portion a first semiconductor region overlapping a second semiconductor region. The first semiconductor region and the second semiconductor region are formed of different semiconductor materials.
1. A method of manufacturing a semiconductor device, comprising:
forming a first stack, wherein the first stack includes first material layers and second material layers that are alternately stacked;
forming a second stack on the first stack, wherein the second stack includes at least one third material layer and at least one fourth material layer;
forming a hole that passes through the first stack and the second stack;
forming a first layer along a sidewall of the hole;
filling a central region of the hole with an insulating material;
opening a portion of the hole passing through the second stack by removing a portion of the insulating material;
forming a second layer along a surface defined by the open portion of the hole, wherein the first layer and the second layer create a first semiconductor layer;
forming a second semiconductor layer along a surface of the second layer, wherein the second semiconductor layer is formed of a semiconductor material that is different from a semiconductor material from which the first semiconductor layer is formed; and
forming a doped semiconductor layer on the second semiconductor layer such that the doped semiconductor layer is spaced from the first semiconductor layer by the second semiconductor layer disposed between the doped semiconductor layer and the first semiconductor layer, wherein the doped semiconductor layer is doped with first conductivity type impurities.
2. The method according to claim 1 , wherein an energy band gap of the second semiconductor layer is less than an energy band gap of the first semiconductor layer.
3. The method according to claim 1 , wherein the first semiconductor layer comprises a silicon layer, and wherein the second semiconductor layer comprises a germanium layer.
4. The method according to claim 1 , further comprising, before the forming of the second layer, etching a portion of the first layer exposed by removing the insulating material.
5. The method according to claim 1 , further comprising diffusing the first conductivity type impurities into the second semiconductor layer and into a portion of the second layer surrounding the second semiconductor layer.
6. The method according to claim 1 , wherein the first conductivity type impurities comprise an n-type dopant.
7. The method according to claim 1 , wherein:
the first and the at least one third material layers define regions in which insulating layers are disposed;
the second material layers define regions in which cell gates are disposed;
the at least one fourth material layer defines a region in which a select gate is disposed; and
the at least one fourth material layer surrounds a portion of a sidewall of the first layer, a portion of a sidewall of the second layer and a portion of a sidewall of the second semiconductor layer.