Vertical transistor and method for fabricating the same
Various embodiments of the present invention disclosure are directed to a vertical transistor having different doping profiles in its upper channel layer and lower channel layer for reducing leakage current while enhancing contact resistance and a method for manufacturing the vertical transistor. According to an embodiment of the present invention disclosure, a semiconductor device comprises a lower contact, a vertical channel layer on the lower contact, the vertical channel layer including a metal component and an oxygen component, and an upper contact on the vertical channel layer. The vertical channel layer has a gradual doping profile in which a doping concentration of the metal component is lowest in an intermediate region and gradually increases from the intermediate region to the upper contact.
1. A vertical transistor comprising:
a lower contact on a substrate;
a channel layer including a lower channel layer, an intermediate channel layer, and an upper channel layer sequentially formed on the lower contact, the channel layer including a metal component and an oxygen component; and
an upper contact on the upper channel layer, wherein
the channel layer has a gradual doping profile in which a doping concentration of the metal component is lowest in the intermediate channel layer and, in the upper channel layer, gradually increases towards the upper contact,
wherein the doping concentration of each metal component doped in the lower channel layer and the intermediate channel layer is maintained uniformly,
wherein the channel layer has an abrupt doping profile in which the doping concentration of the metal component sharply increases at a boundary between the intermediate channel layer and the lower channel layer, and
wherein the lower channel layer is a single layer, and the doping concentration of metal component doped in the lower channel layer is maintained constant throughout the lower channel layer.
2. The vertical transistor of claim 1 , wherein
the channel layer includes at least any one of oxygen (O), indium (In), gallium (Ga), or zinc (Zn).
3. The vertical transistor of claim 1 , wherein
the channel layer is doped with an impurity.
4. The vertical transistor of claim 3 , wherein
the impurity includes silicon (Si) or germanium (Ge).
5. The vertical transistor of claim 1 , wherein
the lower channel layer is formed in a low-concentration oxygen atmosphere, and the intermediate channel layer and the upper channel layer are formed in a high-concentration oxygen atmosphere.
6. The vertical transistor of claim 1 , wherein
the upper channel layer has a constant doping concentration of the metal component at a surface of the upper channel layer, and wherein
the doping concentration of the metal component at the surface of the upper channel layer is the same as that of the upper contact.
7. The vertical transistor of claim 1 , further comprising:
a upper insertion layer on the upper channel layer; and
an upper barrier layer between the upper insertion layer and the upper contact.
8. The vertical transistor of claim 7 , wherein
the upper insertion layer includes indium or an indium-tin compound, and wherein
the upper barrier layer includes titanium (Ti) or titanium nitride.
9. The vertical transistor of claim 7 , further comprising:
a lower barrier layer on the lower contact; and
a lower insertion layer between the lower barrier layer and the lower channel layer.
10. The vertical transistor of claim 9 , wherein
the lower insertion layer includes the same material as the upper insertion layer, and wherein
the lower barrier layer includes the same material as the upper barrier layer.