Method for fabrication of semiconductor device
View Patent ↗After forming a source-drain material film on an insulator layer, an opening portion reaching the insulator layer is formed in the source-drain material film. Then, a channel having desired thickness and a gate insulator are sequentially formed on the insulator layer and the source-drain material film in the opening portion. Thereafter, a gate material film embedding the opening portion is formed on the gate insulator. Subsequently, a cap film is formed on the gate material film, thereby forming the gate made of the gate material film. Then, a mask layer is formed on the source-drain material film. Next, the source-drain material film not protected by the mask layer is removed while protecting the gate by the cap film, thereby leaving the source-drain material film on both sides of the gate. The source-drain material film on one side becomes the source and that on the other side becomes the drain.
1. A method for fabrication of a semiconductor device, comprising the steps of:
(a) forming a source-drain material film on an insulator layer;
(b) forming an opening portion reaching the insulator layer in the source-drain material film;
(c) forming a semiconductor film on the insulator layer in the opening portion and on the source-drain material film in the opening portion;
(d) forming a gate insulator on the semiconductor film;
(e) forming a gate material film embedding the opening portion on the gate insulator;
(f) forming a cap film on the gate material film, thereby forming a gate made of the gate material film;
(g) after the step (f), forming a mask layer on the source-drain material film; and
(h) removing the source-drain material film not protected by the mask layer while protecting the gate by the cap film, thereby leaving the source-drain material film on both sides of the gate.
2. The method for fabrication of a semiconductor device according to claim 1 ,
wherein, in the step (c), the semiconductor film made of an amorphous silicon film is formed.
3. The method for fabrication of a semiconductor device according to claim 2 ,
wherein, before the step (f), the amorphous silicon film is annealed to crystallize the amorphous silicon film.
4. The method for fabrication of a semiconductor device according to claim 3 ,
wherein, in the step (b), the source-drain material film made of a polysilicon film not doped with an impurity is formed, and
after the annealing treatment and before the step (h), an impurity is implanted to the source-drain material film.
5. The method for fabrication of a semiconductor device according to claim 1 ,
wherein, in the step (f), the cap film is formed by deposition.
6. The method for fabrication of a semiconductor device according to claim 1 ,
wherein, in the step (d), the gate insulator made of a silicon oxide film is formed, and
in the step (f), the cap film made of a silicon oxide film deposited by CVD is formed.
7. The method for fabrication of a semiconductor device according to claim 1 ,
wherein, in the step (d), the gate insulator including a nitride film is formed,
in the step (e), the gate material film made of a polysilicon film is formed, and
in the step (f), the cap film made of a silicon oxide film obtained by oxidizing the polysilicon film is formed.
8. The method for fabrication of a semiconductor device according to claim 1 ,
wherein, in the step (e), the gate material film made of a polysilicon film is formed,
after the step (e), a metal film is formed on the gate material film, and
in the step (f), the cap film made of a silicide film obtained by reaction between the polysilicon film and the metal film is formed.