US Patent 7583538 Semiconductor memory and read method of the same

A semiconductor memory including a memory cell which is a MOSFET formed on an SOI substrate. The memory cell has a gate electrode connected to a word line, a drain region connected to a bit line, and a grounded source region. An operation of reading out data written in the memory cell is performed under a biasing condition by which a relationship Vd>Vg−Vth0 holds between a gate voltage Vg to be applied to said gate electrode, a drain voltage Vd to be applied to said drain region, a threshold voltage Vth1 of said MOSFET when a predetermined amount of holes are stored in a body region of the memory cell, and a threshold voltage Vth0 of said MOSFET when holes whose amount is smaller than the predetermined amount are stored in the body region.