Semiconductor storage device capable of improving controllability of density and size of floating gate

A semiconductor storage device comprising:

• a source region and a drain region formed of semiconductor material;
• a channel region located between the source region and the drain region;
• a control gate region formed above the channel region for controlling a channel current flowing through the channel region;
• a first insulating film, a floating gate region and a second insulating film between the channel region and the control gate region;
• wherein the floating gate region comprises a linear region which is continuously formed substantially parallel to the surface of the channel region;
• wherein the floating gate region is the linear region, and the floating gate region is comprised of a polycrystal semiconductor;
• wherein a crystal grain size A in a lengthwise direction and a cross-sectional area S of the linear region of the floating gate region satisfy the conditions:
• q2/(2C)>kT,
• C=2πεiA/log ({(A/2+(A2/4+S2/4){fraction (1/2+L )})}/(S/2))
• and
• εi=(ε1+ε2)/2
• where q is the electron charge, ε1 is a dielectric constant of the first insulating film, ε2 is a dielectric constant of the second insulating film, k is Boltzmann constant and T is a temperature of the semiconductor device.

A semiconductor storage device comprising:

• a source region and a drain region formed of semiconductor material;
• a channel region located between the source region and the drain region;
• a control gate region formed above the channel region for controlling a channel current flowing through the channel region;
• a first insulating film, a floating gate region and a second insulating film between the channel region and the control gate region;
• wherein the floating gate region comprises a linear region which is continuously formed substantially parallel to the surface of the channel region;
• wherein the floating gate region is the linear region, and the floating gate region is comprised of a polycrystal semiconductor;
• wherein a number N of crystal grains in the linear region and a size A of the crystal grain in the lengthwise direction of the linear region satisfy the conditions:
• q(n/LWεi)(t1+(εi/ε1)A/2)>kT/q
• and
• εi=(ε1+ε2)/2
• where q is an electron charge, L is a length of the channel region, w is a width of the channel region, ε1 is a dielectric constant of the first insulating film, ε2 is a dielectric constant of the second insulating film, k is Boltzmann constant, T is a temperature of the semiconductor device, and t1 is a film thickness of the first insulating film.