Semiconductor device having STI with nitride liner and UV light shielding film
A semiconductor device has: a silicon substrate; trench formed downward from the surface of the silicon substrate, the trench defining active regions on the surface of the silicon substrate; a first liner layer of a silicon nitride film covering an inner wall of the trench; a second liner layer of a silicon nitride layer formed on the first liner layer; an element isolation region of an insulator formed on the second liner layer; a p-channel MOS transistor formed in and on one of the active regions; a contact etch stopper layer of a silicon nitride layer not having a ultraviolet shielding ability, formed above the silicon substrate, and covering the p-channel MOS transistor; and a light shielding film of a silicon nitride layer having the ultraviolet shielding ability and formed above the contact etch stopper layer.
1. A semiconductor device comprising:
a silicon substrate;
trench formed downward from a surface of said silicon substrate, said trench defining active regions in the surface of said silicon substrate;
a liner layer of a silicon nitride film covering an inner wall of said trench;
an element isolation region of silicon oxide formed on said liner layer, and filling said trench;
an n-type well formed in one of said active regions, the n-type well being surrounded, in plan view, with said liner layer of the silicon nitride film;
a p-channel MOS transistor formed in and on said n-type well;
a contact etch stopper layer formed on said silicon substrate, directly covering said p-channel MOS transistor;
a lower interlayer insulating film formed on said contact etch stopper layer;
a light shielding film of a Si-rich silicon nitride layer having ultraviolet shielding ability and formed on said lower interlayer insulating layer above said liner layer and said contact etch stopper layer,
an intermediate interlayer insulating film formed on said light shielding film, and having a wiring trench; and
wiring embedded in said wiring trench;
wherein said light shielding film and bottom of said wiring trench have complementary shapes.
2. The semiconductor device according to claim 1 , further comprising
a diffusion preventing layer formed on said intermediate interlayer insulating film and covering said wiring, said diffusion preventing layer having an oxygen intercepting ability and a wiring metal diffusion preventing ability and not having the ultraviolet shielding ability.
3. The semiconductor device according to claim 2 , wherein said wiring is a copper wiring.
4. The semiconductor device according to claim 2 , wherein the intermediate interlayer insulating film does not have the ultraviolet shielding ability.
5. The semiconductor device according to claim 1 , wherein the lower interlayer insulating film is a silicon-oxide-containing insulating layer.
6. The semiconductor device according to claim 5 , wherein the lower interlayer insulating film does not have the ultraviolet shielding ability.
7. The semiconductor device according to claim 1 , wherein the contact etch stopper layer is made of a silicon nitride layer.
8. The semiconductor device according to claim 7 , wherein the silicon nitride layer of said light shielding film has an Si composition larger than an Si composition of the silicon nitride layer of said contact etch stopper layer.
9. The semiconductor device according to claim 1 , further comprising a lower liner layer of a silicon oxide layer covering the inner wall of said trench under said liner layer of the silicon nitride layer.
10. The semiconductor device according to claim 1 , wherein the silicon nitride film of said liner layer has an upper end retracted from the surface of said silicon substrate.
11. The semiconductor device according to claim 1 , wherein the contact etch stopper layer does not have the ultraviolet shielding ability.
12. The semiconductor device according to claim 1 , wherein said element isolation region is formed of silicon oxide.
13. The semiconductor device according to claim 1 , wherein a gate electrode of the p-channel MOS transistor directly overlies said liner of the silicon nitride film.