Threshold detecting method and verify method of memory cells

A method for a reading operation on a memory cell of nonvolatile semiconductor, comprising:

• performing a first sense operation during a first period, the first sense operation including:
• applying a first potential to a gate of a first transistor in order to discharge a potential of a SEN node, the first transistor being electrically connected to the SEN node;
• applying a second potential to a gate of a second transistor in order to stop discharging the potential of the SEN node after applying the first potential, the second transistor being electrically connected to the SEN node;
• and
• applying a third potential to a gate of a third transistor in order to fetch data of the SEN node into a latch circuit in a sense amplifier;
• recharging the SEN node during a second period after the first period, the recharging the SEN node including:
• applying a fourth potential to a gate of a fourth transistor in order to recharge the SEN node;
• and
• performing a second sense operation during a third period, the second sense operation including:
• applying a fifth potential to the gate of the first transistor in order to discharge the potential of the SEN node;
• applying a sixth potential to the gate of the second transistor in order to stop discharging the potential of the SEN node after applying the fifth potential;
• and
• applying a seventh potential to the gate of the third transistor in order to fetch a data of the SEN node into the latch circuit.