Method of fabricating nonvolatile semiconductor memory devices with uniform sidewall gate length
After forming a first dielectric film on the main surface of a semiconductor substrate, a first conductive film is formed on the first dielectric film, and then, the surface of the first conductive film is planarized by a CMP method. Subsequently, the first conductive film and the first dielectric film are etched, thereby forming a select gate having a first gate electrode and a first gate dielectric film. Subsequently, after forming a second dielectric film on the sidewall of the first gate electrode and the main surface, a second conductive film is formed on the second dielectric film, and the second conductive film is etched, thereby forming a memory gate having a second gate electrode and a second gate dielectric film.
1 . A fabricating method of a nonvolatile semiconductor memory device, comprising:
a first dielectric film formed on a main surface of a semiconductor substrate;
a first gate electrode made of a first conductive film formed on said first dielectric film;
a second dielectric film formed on a sidewall of said first gate electrode and said main surface;
a second gate electrode made of a second conductive film formed on said second dielectric film; and
doped regions to be source and drain formed in said semiconductor substrate below said first gate electrode and said second gate electrode,
said fabricating method comprising the steps of:
(a) forming said first dielectric film on said main surface and then forming said first conductive film on said first dielectric film;
(b) planarizing a surface of said first conductive film by a CMP method;
(c) forming said first gate electrode by patterning said first conductive film;
(d) forming said second dielectric film on the sidewall of said first gate electrode and said main surface and forming said second conductive film on said second dielectric film; and
(e) etching back said second conductive film to form said second gate electrode.
2 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein, in said step (d), said second conductive film is formed of amorphous silicon.
3 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein, in said step (d), said second conductive film is formed of amorphous silicon doped with a dopant.
4 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein, in said step (a), said first conductive film is formed of polysilicon not doped with any dopant.
5 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein said second dielectric film is composed of a first oxide film, a trap dielectric film, and a second oxide film formed on the sidewall of said first gate electrode and said main surface, and
said step (d) includes the steps of:
(d1) forming said first oxide film on the sidewall of said first gate electrode and said main surface;
(d2) forming said trap dielectric film on said first oxide film; and
(d3) forming said second oxide film on said trap dielectric film.
6 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein, in said step (c), said first gate electrode is formed so that a gate length of said first gate electrode is set to 120 nm or more.
7 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 ,
wherein, in said step (c), patterning is performed by a photolithography method using KrF light source.
8 . The fabricating method of a nonvolatile semiconductor memory device according to claim 1 , further comprising the step of; (f) forming said doped regions by an ion implantation method with using said second gate electrode as a mask.
9 . A fabricating method of a nonvolatile semiconductor memory device, comprising:
a first dielectric film formed on a main surface of a semiconductor substrate;
a first gate electrode composed of a first conductive film formed on said first dielectric film;
a cap dielectric film formed on said first gate electrode;
a second dielectric film formed on a sidewall of said first gate electrode and said main surface;
a second gate electrode composed of a second conductive film formed on said second dielectric film; and
doped regions to be source and drain formed in said semiconductor substrate below said first gate electrode and said second gate electrode,
said fabricating method comprising the steps of:
(a) forming said first dielectric film on said main surface and then forming said first conductive film on said first dielectric film;
(b) forming said cap dielectric film on said first conductive film;
(c) planarizing a surface of said cap dielectric film by a CMP method;
(d) forming said first gate electrode by patterning said cap dielectric film and said first conductive film;
(e) forming said second dielectric film on the sidewall of said first gate electrode and said main surface and forming said second conductive film on said second dielectric film; and
(f) etching back said second conductive film to form said second gate electrode.
10 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (e), said second conductive film is formed of amorphous silicon.
11 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (e), said second conductive film is formed of amorphous silicon doped with a dopant.
12 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (a), said first conductive film is formed of polysilicon not doped with any dopant.
13 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein said second dielectric film is composed of a first oxide film, a trap dielectric film, and a second oxide film formed on the sidewall of said first gate electrode and said main surface, and
said step (e) includes the steps of:
(e1) forming said first oxide film on the sidewall of said first gate electrode and said main surface;
(e2) forming said trap dielectric film on said first oxide film; and
(e3) forming said second oxide film on said trap dielectric film.
14 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (d), said first gate electrode is formed so that a gate length of said first gate electrode is set to 120 nm or more.
15 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (d), patterning is performed by a photolithography method using KrF light source.
16 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 ,
wherein, in said step (d), said cap dielectric film is formed of silicon oxide.
17 . The fabricating method of a nonvolatile semiconductor memory device according to claim 9 , further comprising the step of: (g) forming said doped regions by an ion implantation method with using said second gate electrode as a mask.