Semiconductor device and method of manufacturing the same

1. A semiconductor device, comprising:

a semiconductor substrate; and

a capacitor structure formed over said semiconductor substrate and structured by the capacitor film being sandwiched between an upper electrode and a lower electrode,

wherein said upper electrode, comprising:

a first layer made of an oxide, of which stoichiometric composition is expressed by a chemical formula M 1 O x1 using a composition parameter x 1 , and of which practical composition is expressed by a chemical formula M 1 O x2 using a composition parameter x 2 ;

a second layer made of an oxide formed on said first layer, and its stoichiometric composition is expressed by a chemical formula M 2 O y1 using a composition parameter y 1 , and its practical composition is expressed by a chemical formula M 2 O y2 using a composition parameter y 2 ; and

a third layer made of an oxide formed on said second layer, and its stoichiometric composition is expressed by a chemical formula M 3 O z1 using a composition parameter z 1 , and its practical composition is expressed by a chemical formula M 3 O z2 using a composition parameter z 2 ,

where the symbols M 1 , M 2 and M 3 are respectively expressed as one or plural metal elements,

wherein said second layer has a degree of oxidation higher than said first layer and said third layer; and

wherein said composition parameters x 1 , x 2 , y 1 , y 2 , z 1 and z 2 have the following relations therebetween,

y 2 /y 1 >x 2 /x 1 , y 2 /y 1 >z 2 /z 1 , and z 2 /z 1 ≧x 2 /x 1 .

2. The semiconductor device according to claim 1 , wherein said metal element M 1 of said first layer and said metal element M 2 of said second layer are the same.

3. The semiconductor device according to claim 1 , wherein said metal element M 1 of said first layer and said metal element M 2 of said second layer differ from each other.

4. The semiconductor device according to claim 1 , wherein said metal element M 1 of said first layer and said metal element M 3 of said third layer are the same.

5. The semiconductor device according to claim 1 , wherein said metal element M 1 of said first layer and said metal element M 3 of said third layer differ from each other.

6. The semiconductor device according to claim 1 , wherein said metal element M 1 of said first layer, said metal element M 2 of said second layer and said metal element M 3 of said third layer differ from each other.

7. The semiconductor device according to claim 1 , wherein said upper electrode further comprises the fourth layer formed above said third layer and made of noble metals or an alloy containing noble metals.

8. The semiconductor device according to claim 1 , wherein the thickness of said first layer is thinner than that of said second layer.

9. The semiconductor device according to claim 1 , wherein the thickness of said third layer is 50 nm or below, thinner than that of said second layer.

10. The semiconductor device according to claim 1 , wherein the crystal size of said first layer is smaller than the crystal size of said second layer.

11. The semiconductor device according to claim 1 , wherein the crystal size of said third layer is smaller than the crystal size of said second layer.

12. The semiconductor device according to claim 1 , wherein said capacitor film is a ferroelectric film.

13. A method of manufacturing the semiconductor device having a capacitor structure comprising:

forming a lower electrode having said capacitor structure over a semiconductor substrate;

forming a capacitor film over said lower electrode; and

forming an upper electrode over said capacitor film by stacking at least a first conductive oxidation layer, a second conductive oxidation layer and a third conductive oxidation layer sequentially,

wherein forming said first conductive oxidation layer and said third conductive layer is conducted under the oxidation content lower than that in depositing said second conductive oxidation layer.

14. The method of manufacturing the semiconductor device according to claim 13 ,

wherein said third conductive oxidation layer is crystallized under controlling the temperature of said semiconductor substrate in forming said third conductive oxidation layer.

15. The method of manufacturing the semiconductor device according to claim 13 , further comprising:

heat treating said capacitor film at a first temperature in a mixture gas atmosphere of inert gas and oxidation gas after depositing said capacitor film and before depositing said first conductive oxidation layer;

heat treating at a second temperature higher than said first temperature in an atmosphere containing oxygen for crystallizing said capacitor film.

16. The method of manufacturing the semiconductor device according to claim 13 , further comprising:

heat treating said capacitor film at a first temperature in a mixture gas atmosphere of inert gas and oxidation gas after depositing said capacitor film and before depositing said first conductive oxidation layer; and

heat treating said capacitor film to crystallize it in an atmosphere containing oxygen at a second temperature higher than said first temperature after depositing said first conductive oxidation layer.

17. The method of manufacturing the semiconductor device according to claim 13 , further comprising:

heat treating said capacitor film after forming said capacitor film and before depositing said first conductive oxidation layer;

depositing an amorphous upper capacitor film thinner than the capacitor film above said crystallized capacitor film; and

heat treating said capacitor film and said upper capacitor film to crystallize them in an atmosphere containing oxygen at a second temperature higher than said first temperature after depositing said first conductive oxidation film.

18. The method of manufacturing the semiconductor device according to claim 13 , further comprising:

heat treating said second conductive oxidation layer in an atmosphere containing oxygen at a third temperature after depositing said second conductive oxidation layer.

19. The method of manufacturing the semiconductor device according to claim 13 , wherein said second conductive oxidation layer is deposited at a temperature in the range of 50° C. to 75° C.

20. The method of manufacturing the semiconductor device according to claim 13 , wherein said capacitor film is a ferroelectric film.