| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor memory device and its manufacturing method. SOLUTION: In a memory cell which is disclosed, a source 120, a drain 118a and a drain 118b which are placed asymmetrically on a semiconductor substrate together with a floating gate core on the semiconductor substrate are lined up. On the side of the source of the memory cell, a source diffusion is not spread so as to exceed an encroachment 116 by a thermal oxide, and it is separated from a floating gate core by a thick oxide in the encroachment. The thick oxide reduces the tunneling of electrons to a minimum on the side of the source. Since the source diffusion and a drain diffusion are arranged asymmetrically, the average dopant density of the source diffusion and that of the drain diffusion are larger than that in a memory cell which is doped asymmetrically in conventional cases. A memory reduces the disturbance of a memory cell adjacent to a memory cell which is programmed, erased or read out. It can affect the programming operation, the erasure operation and the read operation of the memory cell.</p> |
