| 摘要 |
PURPOSE:To improve electric reliability, by forming the third field effect transistor, which connects an external terminal and a drain region, with the same structure as that of the first field effect transistor, thereby suppressing fluctuation in time in threshold voltage. CONSTITUTION:In an input circuit of an EPROM, an electrostatic-breakdown preventing circuit II is provided between an external input terminal BP and an input stage circuit I, which is an internal circuit. The input stage circuit I is constituted by an inverter circuit comprising an N-channel MISFETQn and a P-channel MISFETQp. The electrostatic-breakdown preventing circuit II is constituted by a protecting resistor element R and a clamping MISFETQc. The MISFETQc is composed of a field effect transistor having a floating gate electrode and a control gate electrode. The drain region of the MISFETQc is connected to the external input terminal BP and the input stage circuit I. The source region, the floating gate electrode and the control gate electrode are connected to a reference voltage Vss. The MISFETQc is constituted with the same structure as that of the field effect transistor of a memory cell. |
