Semiconductor integrated circuit device having improved punch-through resistance and production method thereof, semiconductor integrated circuit device including a low-voltage transistor and a high-voltage transistor

摘要

An integrated circuit device comprises a memory cell well formed with a flash memory device, first and second well of opposite conductivity types for formation of high voltage transistors, and third and fourth wells of opposite conductivity types for low voltage transistors, wherein at least one of the first and second wells and at least one of the third and fourth wells have an impurity distribution profile steeper than the memory cell well.