Semiconductor device

1. A semiconductor device comprising:

an active region as a main operation region;

a main electrode film provided on a surface of the active region;

a gate metal electrode pad that is formed on a surface of a rectangular polysilicon layer provided outside the active region;

a multi-stage Zener diode formed in the polysilicon layer in such a manner that multiple stages of p-type layers and n-type layers are alternately formed;

wherein the gate metal electrode pad is formed on the Zener diode with an insulating film interposed in between, one contact region of the Zener diode is electrically connected to the gate metal electrode pad and another contact region is electrically connected to the main electrode film;

wherein the gate metal electrode pad and the main electrode film are electrically connected to the two contact regions of the rectangular Zener diode through contact holes that are formed selectively through the insulating film, at least one pair of contact holes corresponding to the two contact regions are separated from each other in a direction parallel with pn junctions, and the gate metal electrode pad and the main electrode film are isolated from each other between at least the one pair of contact holes.

2. A semiconductor device as claimed in claim 1 , further comprising gate electrodes for controlling a main current flowing through the active region provided on a first major surface of a semiconductor substrate, wherein the gate electrodes extend from plural striped gate electrode polysilicon layers provided on surfaces in the active region, with an insulating film interposed in between, and are connected together to gate metal electrode pad.

3. A semiconductor device as claimed in claim 1 , wherein the main electrode film comprises a source electrode.

4. A semiconductor device as claimed in claim 1 , wherein the main electrode film comprises a drain electrode.

5. A semiconductor device as claimed in claim 1 , wherein the polysilicon layer is substantially rectangular.

6. A semiconductor device as claimed in claim 1 , wherein the Zener diode is substantially rectangular.

7. A semiconductor device as claimed in claim 1 , wherein a breakdown voltage is adjustable by selecting the locations of the contact regions to alter the number of stages provided in the Zener diode.

8. The semiconductor device according to claim 1 , wherein plural multi-stage Zener diodes are formed in the polysilicon layer so as to be isolated from each other and connected to each other in parallel.

9. A semiconductor device comprising:

an active region as a main operation region;

a main electrode film provided on a surface of the active region;

a gate metal electrode pad that is formed inside the active region so as to be electrically isolated from the active region;

plural striped Zener diodes formed in plural respective striped polysilicon layers that are electrically isolated from the plural striped gate electrode polysilicon layers and in each of which p-type layers and n-type layers are formed alternately in multiple stages in a direction that crosses a longitudinal direction of the plural striped polysilicon layers and are connected to each other in series; and

an insulating film which covers surfaces of the striped Zener diodes;

wherein one contact region of each of the striped Zener diodes is electrically connected to the gate metal electrode pad and another contact region of each of the striped Zener diodes is electrically connected to the main electrode film, and the plural striped Zener diodes are connected to each other in parallel.

10. A semiconductor device as claimed in claim 9 , further comprising gate electrodes for controlling a main current flowing through the active region provided on a first major surface of a semiconductor substrate, wherein the gate electrodes extend from plural striped gate electrode polysilicon layers provided on surfaces in the active region with an insulating film interposed in between and are connected together to the gate metal electrode pad.

11. The semiconductor device according to claim 9 , wherein the gate metal electrode pad is formed on the surfaces of the plural striped Zener diodes inside the active region with the insulating film interposed in between.

12. The semiconductor device according to claim 9 , wherein the main electrode film comprises a source electrode.

13. The semiconductor device according to claim 9 , wherein the main electrode film comprises a drain electrode.