Double gate transistor and method of fabricating the same

A method of fabricating a double gate transistor, comprising:

• providing a substrate with a semiconductor layer on its surface;
• forming a patterned hard mask on said semiconductor layer;
• etching said semiconductor layer with the hard mask to form a fin structure, said fin structure having two end portions for forming source and drain regions and a middle portion between said two end portions, side surfaces of said middle portion together with the respective adjacent side surfaces of said two end portions constituting two opposed side surfaces of said fin structure perpendicular to the substrate surface, wherein said middle portion has a width larger than the two end portions for forming source and drain regions;
• depositing gate dielectric and gate materials, so as to form a first stacked layer of the gate dielectric and gate materials on a first side surface of said fin structure, a second stacked layer of the gate dielectric and gate materials on a second side surface of said fin structure, and a third stacked layer of the gate dielectric and gate materials on said hard mask;
• performing planarization by using said hard mask as a stop layer, so as to remove said third stacked layer and maintain said first stacked layer and said second stacked layer on the two opposite side surfaces of said fin structure, wherein the height of said first stacked layer and the height of said second stacked layer are both the same as the height of said middle portion;
• and
• selectively etching the gate dielectric and gate materials in said first stacked layer and said second stacked layer, so as to form a first gate dielectric layer, a second gate dielectric layer, a first gate and a second gate corresponding to said middle portion, such that said middle portion has a length larger than at least one of the first gate and the second gate,
• wherein the length runs along a channel direction, the height runs along a direction perpendicular to the substrate surface, and the width runs along a direction perpendicular to the length and the height, respectively.