Semiconductor device and fabrication method thereof, memory system

A method of forming a semiconductor device, comprising:

• forming a first semiconductor structure comprising a first well region and transistors in the first well region;
• forming a second semiconductor structure comprising a second well region;
• bonding the first semiconductor structure with the second semiconductor structure;
• and
• forming fin field effect transistors in the second well region, wherein each fin field effect transistor comprises a fin structure, a gate oxide layer in contact with a top surface and side surfaces of the fin structure, and a gate layer covering the gate oxide layer.

A memory system, comprising:

• a memory device, comprising:
• a first semiconductor structure comprising a first well region and transistors in the first well region, and
• a second semiconductor structure bonded with the first semiconductor structure and comprising a second well region, and fin field effect transistors in the second well region;
• wherein each fin field effect transistor comprises a fin structure, a gate oxide layer in contact with a top surface and side surfaces of the fin structure, and a gate layer covering the gate oxide layer;
• and
• a controller coupled to the memory device to control the memory device to store data.