Non-volatile semiconductor memory having a ring-shaped floating gate

Abstract

A non-volatile semiconductor memory cell having a novel structure is provided. The memory cell has a ring-shaped channel region formed on a semiconductor substrate, a drain region formed in a zone surrounded by the channel region, and a source region formed outside the channel region. The cell further includes a first gate insulation layer formed on the substrate in such a manner as to cover the boundary between the channel region and the drain region, a ring-shaped floating gate electrode formed on the first gate insulation layer, a second gate insulation layer formed on the floating gate electrode; and a control gate electrode which is capacitive-coupled with the floating gate via the second gate insulation layer.