| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To solve the problem that, in constitution, such as that an EPROM memory cell is equipped with two MOSFETs and data is read by detecting the difference of currents of these MOSFETs, when the data is erased with irradiation of ultraviolet rays, the output of a differential amplifier becomes uncertainty and confirmation of an initialization state is not easy. <P>SOLUTION: In this ultraviolet erasable semiconductor memory, the channel width W<SB>A</SB>of a MOSFET of one side of the two MOSFETs constituting the memory cell is formed narrower than the channel width W<SB>B</SB>of the MOSFET of another side. As a result, the current value I<SB>HA</SB>of the data signal of the MOSFET having the channel width W<SB>A</SB>becomes smaller than the current value I<SB>HB</SB>of the MOSFET having the channel width W<SB>B</SB>in the initialization state in which the memory is irradiated with the ultraviole rays. Thus, the output of the differential amplifier is decided according to the magnitude relation of currents being I<SB>HA</SB><I<SB>HB</SB>and a data value "0" is defined. On the other hand, in writing of data "1", the MOSFET is turned in an OFF state by by raising a threshold Vt while pouring charges into the floating gate electrode 36 of the MOSFET having the channel width W<SB>B</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
