Semiconductor device and method for forming the same
View Patent ↗A semiconductor device includes a trench defined by etching a semiconductor substrate including a device isolation film and an active region, an active region protruded from a side and bottom of the trench, and a gate electrode surrounding the active region simultaneously while being buried in the trench.
1. A semiconductor device comprising:
a trench formed in a device isolation film;
an active region including an expanded end portion protruding from sidewalls and a bottom of the trench; and
a gate electrode disposed over an upper surface and sidewalls of the expanded end portion and buried in the bottom of the trench.
2. The semiconductor device according to claim 1 , wherein a second width of the expanded end portion is greater than a first width of the active region.
3. The semiconductor device according to claim 2 , wherein the expanded end portion includes an expanded part with the second width, and a neck part with the first width between the expanded part and outer surfaces of the device isolation film defining a space between the expanded part and an outer surface of the device isolation film in the trench.
4. The semiconductor device according to claim 3 , wherein portions of the gate electrode are disposed in the space.
5. The semiconductor device according to claim 1 , wherein a channel region is formed over sidewalls and upper surface of the expanded end portion.
6. A method for forming a semiconductor device comprising:
forming a trench by etching a semiconductor substrate including a device isolation film and an active region;
forming a first protrusion part by etching the device isolation film so that the active region protrudes from surfaces of the trench;
forming a second protrusion part by growing the first protrusion part;
forming an expanded end portion by etching portions of the device isolation film adjacent to the second protrusion part; and
forming a gate electrode over a bottom surface of the trench surrounding the expanded end portion.
7. The method according to claim 6 , wherein the expanded end portion includes an expanded part with the second width, and a neck part with the first width between the expanded part and outer surfaces of the device isolation film defining a space between the expanded part and an outer surface of the device isolation film in the trench.
8. The method according to claim 6 , wherein forming the first protrusion part includes anisotropically etching the device isolation film.
9. The method according to claim 8 , wherein the second protrusion part is grown by an epitaxial growth process.
10. The method according to claim 6 , wherein the second protrusion part and the expanded end portion has a larger width than the active region.
11. The method according to claim 6 , wherein forming the gate electrode includes:
burying a metal layer in the trench; and
etching back the metal layer.