Method of manufacturing semiconductor device

A method of manufacturing a semiconductor device, comprising:

• forming a fin on a semiconductor substrate, wherein the fin comprises first sacrificial layers and channel layers alternately stacked in a thickness direction of the semiconductor substrate, and second sacrificial layers and a third sacrificial layer alternately stacked in the thickness direction of the semiconductor substrate;
• the alternately stacked first sacrificial layers and the channel layers are located on both sides of the alternately stacked second sacrificial layers and the third sacrificial layer in the thickness direction of the semiconductor substrate;
• a bottom film layer and a top film layer among the alternately stacked first sacrificial layers and the channel layers are the first sacrificial layers, and a bottom film layer and a top film layer among the alternately stacked second sacrificial layers and the third sacrificial layer are the second sacrificial layers;
• forming a mask straddling the fin;
• selectively removing the second sacrificial layers to form a first dielectric filling region;
• forming first middle dielectric isolation layers in the first dielectric filling region;
• removing the first sacrificial layers, the channel layers, the first middle dielectric isolation layers, and the third sacrificial layer not covered by the mask;
• forming a first source region and a first drain region on both sides of the remaining first sacrificial layers and channel layer located below the remaining first middle dielectric isolation layers, respectively;
• forming an insulating layer on the first source region and the first drain region;
• and
• forming a second source region and a second drain region on the insulating layer and on both sides of the remaining first sacrificial layers and channel layer located above the remaining first middle dielectric isolation layers, respectively,
• wherein a conductivity type of the second source region and the second drain region is opposite to a conductivity type of the first source region and the first drain region.