Method of manufacturing semiconductor device

A method of manufacturing a semiconductor device, the method comprising:

• forming a stack;
• forming an opening in the stack;
• forming an amorphous silicon layer in the opening;
• forming a capping layer on the amorphous silicon layer, the capping layer including a first section having a first thickness and a second section having a second thickness thicker than the first thickness;
• doping the capping layer with metal, including a first doping concentration difference between the first section and the second section;
• doping the amorphous silicon layer, including a second doping concentration difference between a third section and a fourth section by diffusing the metal through the capping layer, wherein the second doping concentration difference is smaller than the first doping concentration difference;
• and
• forming a polysilicon layer by crystallizing the amorphous silicon layer using the metal as a seed.

A method comprising:

• forming a preliminary channel layer in a hole in a stack;
• forming a capping layer on the preliminary channel layer, wherein the capping layer has a varying thickness;
• forming metal seeds in the capping layer;
• diffusing the metal seeds into the preliminary channel layer through the capping layer;
• and
• forming a channel layer by crystallizing the preliminary channel layer using the metal seeds.