Nonvolatile semiconductor memory transistor, nonvolatile semiconductor memory, and method for manufacturing nonvolatile semiconductor memory

A nonvolatile semiconductor memory transistor comprising:

• an island-shaped semiconductor having a source region, a channel region, and a drain region in order from surface of a substrate;
• a hollow pillar-shaped floating gate surrounding an outer periphery of the channel region and a tunnel insulating film between the floating gate and the channel region, the hollow pillar-shaped floating gate having a circumferential recess therein;
• and
• a hollow pillar-shaped control gate surrounding an outer periphery of the floating gate and at least partially within the circumferential recess;
• and
• an inter-polysilicon insulating film residing in the circumferential recess between the control gate and the floating gate,
• wherein the inter-polysilicon insulating film resides between the floating gate and an upper surface, a lower surface, and a lateral side surface of the control gate,
• wherein the control gate faces the floating gate in the recess and the lateral side surface of the control gate does not face the island-shaped semiconductor in a vertical direction, and
• wherein the upper surface of the floating gate does not face the island-shaped semiconductor in the vertical direction.