Regulator circuit and semiconductor device therewith

Abstract

A regulator circuit including an output-stage transistor for supplying a current to an external circuit has an electrostatic protection transistor formed in parallel with the output-stage transistor. The base of the electrostatic protection transistor is connected to, for example, the base of the output-stage transistor, or alternatively to a ground line or to the emitter of the electrostatic protection transistor itself.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of the regulator system of a first embodiment of the present invention;

FIG. 2 is a diagram showing the cross-sectional structure of the output-stage transistor and the electrostatic protection transistors shown in FIG. 1;

FIG. 3 is a diagram showing the arrangement of the electrostatic protection transistor shown in FIG. 1 on the substrate;

FIG. 4 is a diagram showing the positional relationship between the output-stage transistor and the electrostatic protection transistor shown in FIG. 1 on the substrate;

FIG. 5 is a diagram showing another example of the cross-sectional structure of the output-stage transistor and the electrostatic protection transistor shown in FIG. 1;

FIG. 6 is a circuit diagram of the regulator system of a second embodiment of the present invention;

FIG. 7 is a circuit diagram of the regulator system of a third embodiment of the present invention;

FIG. 8 is a circuit diagram showing a modified example of the regulator system shown in FIG. 7;

FIG. 9 is an example of the circuit of a conventional regulator system; and

FIG. 10 is another example of the circuit of a conventional regulator system.

Claims

1. A regulator circuit including an output-stage transistor for supplying a current to an external circuit, wherein an electrostatic protection transistor is formed in parallel with the output-stage transistor.

2. The regulator circuit according to claim 1, wherein an emitter, a base, and a collector of the electrostatic protection transistor are connected respectively to an emitter, a base, and a collector of the output-stage transistor.

3. The regulator circuit according to claim 1, wherein an emitter and a collector of the electrostatic protection transistor are connected respectively to an emitter and a collector of the output-stage transistor, andwherein a base of the electrostatic protection transistor is connected to a reference potential point.

4. The regulator circuit according to claim 1, wherein an emitter and a collector of the electrostatic protection transistor are connected respectively to an emitter and a collector of the output-stage transistor, andwherein a base and the emitter of the electrostatic protection transistor are connected together.

5. A semiconductor device incorporating a regulator circuit including an output-stage transistor for supplying a current to an external circuit, wherein the output-stage transistor and an electrostatic protection transistor are formed on a semiconductor substrate, andwherein the electrostatic protection transistor is formed in parallel with the output-stage transistor.

6. The semiconductor device according to claim 5, wherein an emitter area of the electrostatic protection transistor is smaller than an emitter area of the output-stage transistor.

7. The semiconductor device according to claim 6, wherein the emitter area of the electrostatic protection transistor is equal to or smaller than one-tenth of the emitter area of the output-stage transistor.

8. The semiconductor device according to claim 5, wherein the output-stage transistor and the electrostatic protection transistor are formed on the semiconductor substrate while being separated by an element separation region, andwherein a space between a base and a collector of the electrostatic protection transistor, a space between an emitter and the base of the electrostatic protection transistor, a space between the base of the electrostatic protection transistor and part of the element separation region closest thereto, and a space between the collector of the electrostatic protection transistor and part of the element separation region closest thereto are larger respectively than comparable spaces in the output-stage transistor.

9. The semiconductor device according to claim 5, wherein a base impurity concentration of the electrostatic protection transistor is lower than a base impurity concentration of the output-stage transistor.

10. The semiconductor device according to claim 5, wherein an emitter of the electrostatic protection transistor is formed deeper than an emitter of the output-stage transistor.

11. The semiconductor device according to claim 5, wherein, as seen from above the semiconductor substrate, an emitter, a base, and a collector of the electrostatic protection transistor are each given an exterior shape including a curve.

12. The semiconductor device according to claim 11, wherein the exterior shape of each of the emitter, the base, and the collector of the electrostatic protection transistor is circular.

13. The semiconductor device according to claim 5, wherein, in the electrostatic protection transistor, a contact of an emitter thereof and a contact of a collector thereof are adjacent to each other.

14. The semiconductor device according to claim 5, wherein the electrostatic protection transistor is arranged adjacent to an output pad via which an output current from the output-stage transistor is fed out.

15. The semiconductor device according to claim 5, wherein the electrostatic protection transistor is arranged between an output pad via which an output current from the output-stage transistor is fed out and a region where the output-stage transistor is formed.

16. A method for fabricating a semiconductor device incorporating a regulator circuit including an output-stage transistor for supplying a current to an external circuit, the method comprising: a first step of forming the output-stage transistor and an electrostatic protection transistor on a semiconductor substrate, anda second step of forming a diffusion resistor in the semiconductor device,wherein the electrostatic protection transistor is formed in parallel with the output-stage transistor,wherein a base impurity concentration of the electrostatic protection transistor is made lower than a base impurity concentration of the output-stage transistor, andwherein a base of the electrostatic protection transistor is formed by the second step.