Semiconductor element, electronic system including the semiconductor element, and method of fabricating the semiconductor element

A semiconductor element comprising:

• a substrate comprising a trench, a source region, and a drain region,
• the source region and the drain region separated apart from each other by the trench;
• a gate insulating layer covering a bottom surface and a sidewall of the trench;
• a gate electrode comprising a lower buried portion and an upper buried portion with the gate insulating layer therearound,
• the lower buried portion filling a lower region of the trench, and
• the upper buried portion being on the lower buried portion and filling an upper region of the trench;
• and
• a capping layer on the gate electrode,
• wherein the lower buried portion comprises a barrier layer and a first conductive layer,
• the barrier layer is in the trench,
• the barrier layer covers a bottom surface of the gate insulating layer and a lower region of a sidewall of the gate insulating layer,
• the barrier layer surrounds the first conductive layer,
• the first conductive layer fills the lower region of the trench, and
• the lower buried portion does not overlap the source region and the drain region, and
• wherein the upper buried portion comprises a two-dimensional material layer and a second conductive layer,
• the two-dimensional material layer is in the trench,
• the two-dimensional material layer covers an upper surface of the first conductive layer and an upper region of the sidewall of the gate insulating layer,
• the two-dimensional material layer surrounds the second conductive layer,
• the second conductive layer fills the upper region of the trench,
• the upper buried portion overlaps the source region and the drain region, wherein the two-dimensional material layer directly contacts the gate insulating layer, and
• wherein a first dielectric constant of a lower region of the gate insulating layer is greater than a second dielectric constant of an upper region of the gate insulating layer.

A semiconductor element comprising:

• a substrate comprising a trench, a source region, and a drain region,
• the source region and the drain region separated apart from each other by the trench;
• a gate insulating layer covering a bottom surface and a sidewall of the trench;
• a gate electrode comprising a barrier layer, a two-dimensional material layer, and a conductive layer;
• and
• a capping layer on the gate electrode,
• wherein the gate insulating layer surrounds the barrier layer,
• the barrier layer is in the trench,
• the barrier layer covers a bottom surface of the gate insulating layer and a lower region of a sidewall of the gate insulating layer,
• the two-dimensional material layer covers an upper region of the sidewall of the gate insulating layer in the trench, and
• the conductive layer is in the trench and includes a first conductive layer surrounded by the barrier layer and a second conductive layer surrounded by the two-dimensional material layer,
• wherein the barrier layer does not overlap the source region and the drain region, and
• the two-dimensional material layer overlaps the source region and the drain region,
• a material in the first conductive layer is different from a material in the second conductive layer, and
• wherein a first dielectric constant of a lower region of the gate insulating layer is greater than a second dielectric constant of an upper region of the gate insulating layer.