Dual work function buried gate-type transistor, method for forming the same, and electronic device including the same

A transistor comprising:

• a source region and a drain region that are formed in a substrate and spaced apart from each other;
• a trench formed in the substrate between the source region and the drain region;
• and
• a buried gate electrode disposed in the trench,
• wherein the buried gate electrode comprises:
• a lower buried portion which includes a high work-function barrier layer and a first low-resistivity layer disposed over the high work-function barrier layer, wherein the high work-function barrier layer includes aluminum-containing titanium nitride;
• and
• an upper buried portion which includes a low work-function barrier layer and a second low-resistivity layer, wherein the second low-resistivity layer is disposed over the first low-resistivity layer and located substantially at the same level as the source region and the drain region, wherein the low work-function barrier layer extends between the second low-resistivity layer and the source region and further extends between the second low-resistivity layer and the drain region.