MOS TYPE SEMICONDUCTOR DEVICE
A MOS type semiconductor device, in which both improvement in radiation resistance and increase in withstand voltage is achieved, includes a nitride film formed on a LOCOS film and a PBSG film formed on the nitride film. The refractive index of the nitride film is set in a range of from 2.0 to 2.1 and the thickness of the nitride film is set in a range of from 0.1 Am to 0.5 μm to thereby provide the nitride film as a semi-insulative thin film. Of electron-hole pairs produced in the LOCOS film by γ-ray irradiation, holes low in mobility are let away to a source electrode via the nitride film to thereby suppress the amount of plus fixed electric charges stored in the LOCOS film. The provision of such a three-layer structure permits improvement in radiation resistance and increase in withstand voltage.
1 . An MOS type semiconductor device comprising:
a semiconductor substrate;
an insulating film disposed on the semiconductor substrate; and
a thin film disposed on the insulating film so as to be lower in resistivity than the insulating film,
wherein the thin film is electrically connected to a source electrode.
2 . The MOS type semiconductor device according to claim 1 , wherein the insulating film is one of a LOCOS film and a thermal oxide film.
3 . The MOS type semiconductor device according to claim 1 , wherein the thin film is disposed so that a source portion and a drain portion disposed on the semiconductor substrate to form the MOS type semiconductor device are surrounded by the thin film.
4 . The MOS type semiconductor device according to claim 1 , wherein the thin film has such a resistivity that a current of 1 pA to 1 nA flows when a rating voltage is applied between the source electrode and the drain electrode.
5 . The MOS type semiconductor device according to claim 4 , wherein the thin film is a semi-insulative thin film.
6 . The MOS type semiconductor device according to claim 5 , wherein the semi-insulative thin film is one of a nitride film and a film capable of producing negative fixed electric charges and has a refractive index of 2.0 to 2.1.
7 . The MOS type semiconductor device according to claim 4 , wherein the thin film is a conductive thin film.
8 . The MOS type semiconductor device according to claim 7 , wherein the conductive thin film is one of a carbon thin film and a high melting point metal thin film and has an average thickness of 0.1 nm to 0.5 nm.
9 . The MOS type semiconductor device according to claim 8 , wherein the high melting point metal thin film is any one of a tungsten thin film, a titanium thin film and a chromium thin film.
10 . The MOS type semiconductor device according to claim 1 , wherein a second insulating film higher in resistivity than the thin film is formed on the insulating film through the thin film.
11 . An MOS type semiconductor device comprising:
a semiconductor substrate;
an insulating film disposed on the semiconductor substrate; and
a thin film disposed on the insulating film so as to be lower in resistivity than the insulating film,
wherein the thin film is electrically connected to a source electrode or to both the source electrode and a drain electrode.
12 . The MOS type semiconductor device according to claim 11 , wherein the insulating film is one of a LOCOS film and a thermal oxide film.
13 . The MOS type semiconductor device according to claim 11 , wherein the thin film is disposed so that a source portion and a drain portion disposed on the semiconductor substrate to form the MOS type semiconductor device are surrounded by the thin film.
14 . The MOS type semiconductor device according to claim 11 , wherein the thin film has such a resistivity that a current of 1 pA to 1 nA flows when a rating voltage is applied between the source electrode and the drain electrode.
15 . The MOS type semiconductor device according to claim 14 , wherein the thin film is a semi-insulative thin film.
16 . The MOS type semiconductor device according to claim 15 , wherein the semi-insulative thin film is one of a nitride film and a film capable of producing negative fixed electric charges and has a refractive index of 2.0 to 2.1.
17 . The MOS type semiconductor device according to claim 14 , wherein the thin film is a conductive thin film.
18 . The MOS type semiconductor device according to claim 17 , wherein the conductive thin film is one of a carbon thin film and a high melting point metal thin film and has an average thickness of 0.1 nm to 0.5 nm.
19 . The MOS type semiconductor device according to claim 18 , wherein the high melting point metal thin film is any one of a tungsten thin film, a titanium thin film and a chromium thin film.
20 . The MOS type semiconductor device according to claim 11 , wherein a second insulating film higher in resistivity than the thin film is formed on the insulating film through the thin film.