JP3178855B2 - Semiconductor element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output circuit in a semiconductor device, and more particularly to a protection circuit for the output circuit.

[0002]

2. Description of the Related Art In a semiconductor device, a protection element is provided in an input / output section in order to protect the internal element from damage caused by external static electricity or the like. FIG. 3 shows a conventional diode-clamp protection circuit (equivalent circuit), and FIG. 4 shows an element configuration. When a high voltage is applied to the output pad from the outside, that is, a high voltage is applied to the output drains 2 and 3 in FIG.
A high voltage is applied to a gate oxide film between gate electrodes 5 of (MOS transistors). However, the applied voltage is clamped by the respective diode withstand voltages at the two or three drain portions, and only the voltage corresponding to the withstand voltage is applied to the gate film. Further, although the voltage is clamped, a current flows from each drain to GND and the power supply.

The output element is protected by the clamped voltage and current and the resistance of the output element.

[0004]

However, in the above-described configuration, the resistance of the output element is reduced as the element is miniaturized. That is, in a device having a gate oxide film thickness of 100 °, it is necessary to control the clamp voltage to about 10 V or less.
In the case of r, in order to obtain Hot Electron resistance, the LDD structure and the DDD structure, on the contrary, the drain breakdown voltage is improved. Therefore, it is difficult to obtain the above-described effects.

An object of the present invention is to provide a protection element which protects an output section composed of a fine Tr as described above.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a dummy element is provided between an output element and an output pad to prevent destruction and deterioration due to external noise in an output element of a semiconductor device. And a junction having a lower withstand voltage than the first drain, which is a main function of the output element, is provided in the element having the Tr structure and the second drain near one of the outputs.

[0007]

As described above, according to the present invention, the dummy gate electrode and the drain portion having a withstand voltage lower than the drain withstand voltage of the output Tr are provided between the output element and the output pad. Degradation due to leakage and the like can be prevented.

[0008]

FIG. 1 is a structural view of an embodiment of an output element and a protection element according to the present invention, and FIG. 5 is an equivalent circuit thereof. The N-channel transistor of the output element is mainly composed of the source part 6, the first drain part 7 and the gate part 14, and the P-channel transistor is composed of the source part 11, the first drain part 10 and the gate part 17. And their output PAD sides respectively have 8, 9 second drain sections and 1
5 and 16 dummy gate electrode portions are provided.
Also, these 7, 8, 15 and 9, 16, 10 are connected to the output PAD by metal wiring to obtain the same potential.
(Omitted in the configuration diagram of FIG. 1) Also, each second drain 8, 9 of the output transistor is connected to each first drain 7, 1
The drain portion is formed with a junction breakdown voltage lower than zero.

The high voltage such as static electricity that enters the semiconductor device from the outside is generated by the second drains 8 and 9 of the output unit.
The voltage is clamped and the current flows to GND or the power supply. Therefore, the applied voltage and current to the transistor portion having the output function are controlled, and the destruction and deterioration of the output element can be prevented. Further, each of the dummy gate electrodes 15 and 16 is provided to reduce the second drain voltage. The breakdown voltage of each junction is determined by the impurity concentration of the semiconductor in contact with it and the impurity concentration of the corresponding junction,
It can be set by the junction depth and the impurity profile in the vicinity of the junction surface. When formed by the gate electrode and the corresponding junction, that is, the portion A shown in FIG. 2 has the lowest junction breakdown voltage. The junction withstand voltage may be set as low as the upper limit of the voltage operation range in the semiconductor device.

[0010]

As described above, according to the present invention, a dummy gate electrode and a drain portion having a withstand voltage lower than the drain withstand voltage of the output Tr are provided between the output element and the output pad. Further, it is possible to prevent deterioration such as leakage due to electron injection.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view of a joint.

FIG. 3 is an equivalent circuit diagram of a conventional output unit.

FIG. 4 is a configuration diagram of a conventional output circuit unit.

FIG. 5 is an equivalent circuit diagram of the embodiment of the present invention.

[Explanation of symbols]

 8 N-channel output transistor second drain section 9 P-channel output transistor second drain section 15 N-channel output transistor dummy electrode 17 P-channel output transistor dummy electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 29/78 (58) Investigated field (Int.Cl. ⁷ , DB name) H01L 27/06 H01L 27/08 H01L 27/088 -27/092

Claims (3)

(57) [Claims] 1. A semiconductor device having a first output transistor connected between a first potential and an output terminal, wherein: a first source connected to a first drain of the first output transistor; A first protection transistor having a withstand voltage lower than the withstand voltage of the first protection transistor and having a second drain connected to the output terminal, and a first gate connected to the first source and the second drain. A semiconductor element characterized by the above-mentioned. 2. The semiconductor device according to claim 1, wherein: a second output transistor connected between a second potential and the output terminal; and a second source connected to a third drain of the second output transistor. And a fourth protection transistor having a breakdown voltage lower than the breakdown voltage of the third drain, and having a fourth drain connected to the output terminal, and a gate connected to the second source and the fourth drain. 2. The semiconductor device according to claim 1, comprising: 3. A P-channel output transistor connected between a power supply potential and an output terminal, an N-channel output transistor connected between a ground potential and the output terminal, and the P-channel output transistor. And a N-channel protection transistor connected between the N-channel output transistor and the output terminal, wherein the P-channel protection transistor is connected between the P-channel protection transistor and the output terminal. type and N-channel type protective transistor is formed in the third region between the P-channel type output second region where the transistor is the N-channel output transistor and the first region formed is formed, the The source region of the P-channel type protection transistor is
The source region of the N-channel protection transistor is the same region as the drain region of the P-channel output transistor.
Semiconductor wherein a same region and the drain region of the N-channel type output transistor, a wiring, the drain region of each of the P-channel and N-channel output transistor, characterized in that connected to the output terminal element.