Nonvolatile semiconductor storage device
View Patent ↗In order to provide a nonvolatile semiconductor storage device designed to take off such existing restraint on the degree of freedom of device design as needed for the purpose of securing design margin, thus realizing a ferroelectric, nonvolatile storage device of high integration density, there is disclosed a capacitor using a ferroelectric thin film is provided, so that the apparent coercive electric field value in the operational guaranteed margin temperature of the nonvolatile semiconductor storage device when regarded as the voltage applied to the capacitor remains within the range of design margin of the nonvolatile semiconductor storage device at the coercive electric field value at the specified temperature, in which a metal oxide of a layer structure having the ferroelectric-to-normal dielectric phase transition point of 800° C. or higher may be used for the ferroelectric thin film.
1. A nonvolatile semiconductor storage device comprising:
a complex capacitor comprised of a dielectric thin film having a temperature dependency, in which a dielectric constant of the capacitor decreases an increase in temperature in an operational temperature range of said nonvolatile semiconductor storage device, and a ferroelectric capacitor provided having a ferroelectric thin film.
2. The nonvolatile semiconductor storage device according to claim 1 , wherein:
said complex capacitor comprises a complex thin film having a ferroelectric property rendered by a compounding action of the dielectric thin film having a temperature dependency wherein the dielectric constant decreases accompanying an increase in temperature in the operational temperature range of said nonvolatile semiconductor storage device, the ferroelectric thin film exhibiting the ferroelectric property in the operational temperature range, and a conductive thin film held between said dielectric thin film and said ferroelectric thin film.
3. The nonvolatile semiconductor storage device according to claim 1 , wherein:
said dielectric thin film has the temperature dependency in which the dielectric constant decreases accompanying an increase in temperature in the operational temperature range of said nonvolatile semiconductor storage device and further comprising a relaxation type ferroelectric thin film.
4. The nonvolatile semiconductor storage device according to claim 2 , wherein:
said dielectric thin film has a temperature dependency in which the dielectric constant decreases an increase in temperature in the operational temperature range of said nonvolatile semiconductor storage device.
5. The nonvolatile semiconductor storage device according to claim 3 , wherein:
said relaxation type ferroelectric thin film comprises a metal oxide having a Perovskite structure.
6. The nonvolatile semiconductor storage device according to claim 4 , wherein:
said relaxation type ferroelectric thin film comprises a metal oxide having a Perovskite structure.
7. The nonvolatile semiconductor storage device according to claim 1 , wherein:
said ferroelectric thin film being selected from the group consisting of PZT expressed by Pb(Zr x Ti 1−x )O 3 (where 0.1≦x≦0.8), PZT added with La or Nb, and PZT part of Pb of which is substituted by La or part of (Zr, Ti) of which is substituted by Nb.
8. The nonvolatile semiconductor storage device according to claim 2 , wherein:
said ferroelectric thin film comprises any one of PZT expressed by Pb (Zr x Ti 1−x )O 3 (where 0.1≦x≦0.8), PZT added with La or Nb, and PZT part of Pb of which is substituted by La or part of (Zr, Ti) of which is substituted by Nb.
9. The nonvolatile semiconductor storage device according to claim 1 , wherein:
said ferroelectric thin film comprises any one of Sr 1−x Bi 2+x Ta 2 O 9 (where 0.01≦x≦0.3), Sr 1−x Bi 2+x Nb 2 O 9 (where 0.01≦x≦0.3) and Sr 1−x Bi 2+x (Ta 1−y Nb y )O 9 (where 0.01≦x≦0.3, 0.1≦y≦0.5).
10. The nonvolatile semiconductor storage device according to claim 2 , wherein:
said ferroelectric thin film comprises any one of Sr 1−x Bi 2+x Ta 2 O 9 (where 0.01≦x≦0.3), Sr 1−x Bi 2+x Nb 2 O 9 (where 0.01≦x≦0.3) and Sr 1−x Bi 2+x (Ta 1−y Nb y )O 9 (where 0.01≦x≦0.3, 0.1≦y≦0.5).
11. The nonvolatile semiconductor storage device according to claim 1 , wherein:
connection between said dielectric capacitor and said ferroelectric capacitor of said complex capacitor is made with any one of a metal and a conductive metal oxide.