Transistor of semiconductor device and method for fabricating the same

A method for fabricating a transistor comprising:

• forming a first source or drain region by a first ion implantation process on a semiconductor substrate;
• depositing a first sacrificial layer over the semiconductor substrate, and dry etching a portion of the sacrificial layer to form a hole which exposes the first source or drain region;
• depositing and flattening a first conducting layer over the first sacrificial layer to form a channel region filling the hole;
• removing the first sacrificial layer;
• forming a second sacrificial layer over the first source and drain region and the channel region;
• performing a second ion implanting process on the channel region;
• removing the second sacrificial layer;
• forming a gate insulation layer over the channel region forming a gate conducting layer;
• dry etching the gate conducting layer to form a gate conductor extending over an upper portion and one side of the channel region;
• implanting ions to form a second source and drain region over the channel region;
• forming an intercalary insulation layer over the semiconductor substrate;
• etching the intercalary insulation layer to form contact holes exposing a portion of the first and second source and drain regions and the gate conductor;
• and
• depositing and patterning a second conducting layer over the intercalary insulation layer to fill the contact holes.