| 摘要 |
<p>PURPOSE:To easily measure the threshold voltage of a memory transistor by providing a boosting function for boosting a voltage value impressed on the gate of a selecting transistor to a voltage value higher than a voltage value obtained by adding the threshold voltage of the selecting transistor to a voltage impressed to an external input terminal. CONSTITUTION:When a test control signal TE goes to an 'H' level, a writing control circuit 5 drives to boost a Y gate line YL, a word line WL selected by a column decoder 4 and a row decoder 3 to a VPP level by high voltage VPP switches 6a, 6b. Accordingly, the VPP level is impressed to the gates of the respective selecting transistors Q1, Q2, Q4, Q5 of the memory transistor Q3 in a selected memory cell 1. Thereby, since the required maximum value of a test voltage Vtest transferred to a control line CL is not higher than the VPP, the voltage value can be applied to the control gate of the memory transistor Q3 through the selecting transistors Q4, Q1 without damaging the value and the threshold voltage of the erased memory transistor can be completely measured.</p> |
