JPS61216477A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the withstand voltage for an external surge voltage by connecting part of the control electrode of an output transistor with the prescribed potential for setting the transistor in the portion in nonconductive state. CONSTITUTION:When a surge voltage which exceeds the withstand voltage of an output transistor Q1 is applied externally if output transistors Q1, Q2 are in nonconductive state, the surge voltage is applied from metal wirings 14 connected with an output terminal 21 to transistors Q1, Q3 is flowed through the channel of the gate electrode 12 for driving the transistor Q1 to its source, but also flowed simultaneously to the channel of the gate electrode 13 of the protecting transistor Q3 fixed to the ground potential. Accordingly, as a result, a current amount per unit channel area is reduced, and the terminal 21 is endured for a larger surge voltage. Thus, the current amount flowed per unit area of the output transistor reduces to improve the protecting function of the output terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device provided with a barrier, particularly a surge voltage protection device applied to an output terminal of the semiconductor device.

Note that the following description will be made regarding an MO8 type semiconductor device in which this surge voltage application is particularly problematic.

[Conventional technology]

Conventionally, the output terminal of an MOa type semiconductor device does not particularly require protection against external surge voltage because the output MO8 transistor that activates the output terminal has a partially large channel width.

[Problem that the invention seeks to solve]

However, with the recent increase in the degree of high-level integration of semiconductor devices, the junction depth of impurity diffusion regions has decreased, channels have become shorter, etc., and the withstand voltage of output transistors has decreased, causing damage due to external surge voltage. It's getting easier.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device that can improve the withstand voltage against external surge voltage, which has been a problem with the conventional output circuits described above.

[Means for solving problems]

The semiconductor device of the present invention has a transistor connected to the output terminal in a non-conducting state and at a negative potential.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a main part of an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram thereof, and FIG. 1 is a transistor (
h, shows the Qs part.

In this example, metal distribution! A gate electrode 12 connected to the output terminal 21 by 14 and divided into six pieces, l
3' is connected to the ground potential GND via an N-channel MOS transistor. That is, the grounded portion of the gate electrode 13 connects the power supply Vcc source of the protection transistor Q3 shown in FIG. 2 to the output transistor connected to the drain of the output transistor Q1.

Here, when the output transistors Ql and Q2 are in a non-conducting state, when a surge voltage is applied from the outside that causes the withstand voltage of the output transistor Q1, the metal wiring 14 connected to the aha terminal 21) transistor Q1. A surge voltage is applied to Qa. The charge added to the drain part of the transistor (h, Q3) flows into the source through the channel part of the output transistor Q!t-driving gate electrode 12, or at the same time flows into the gate electrode 13 of the protective transistor Q3 fixed to the ground potential. Because it also flows to the channel part of
As a result, the amount of current per unit channel area is reduced, allowing the output terminal 21 to withstand larger surge voltages.

Note that the above embodiment uses an N-channel M transistor as a transistor.
Although the present invention is directed to the U8 transistor, it goes without saying that the present invention is not limited thereto and is applicable to P-channel MO8 transistors, and more generally to all transistors including bipolar transistors.

〔Effect of the invention〕

As described in detail above, according to the present invention, when the external surge voltage applied to the output terminal exceeds the withstand voltage of the output transistor, it also flows to the protection transistor that fixes the output circuit to the configuration potential.

Therefore, a semiconductor device can be obtained in which the amount of current flowing per unit area of the output transistor is small and the ability to protect the output terminal is improved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing essential parts of an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram thereof. 11...N-type diffusion region, 12.13...
・Gate electrode, 14.15...Metal wiring, 16
...Input signal line, 17...Contact hole, 21...Output terminal, 22.23...
...Input signal terminal, Q 1 * Q 2 ... Output transistor s Qs ... Protection transistor, Vcc ... Power supply, GND ... Ground potential.

Claims (1)

[Claims] A part of the control electrode of an output transistor connected to an output terminal and having a control electrode divided into a plurality of parts is connected to a constant potential that makes the output transistor in that part non-conductive. Semiconductor equipment.