SEMICONDUCTOR DEVICE

Abstract

A semiconductor device for improving performance of a p-channel transistor and an n-channel transistor having multi-finger structures. Gates of the n-channel transistor are arranged so that their gate width direction is parallel to one side of a first region. Gates of the p-channel transistor are arranged so that their gate width direction extends at an angle of 45 degrees with respect to one side of a second region. The ratio of a maximum gate width of the p-channel transistor arranged in the second region to the pitch between the gates of the p-channel transistor is set in accordance with the ratio of the area of an ineffective region to the area of the second region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic layout diagram showing a semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a schematic plan view of a p-channel transistor having a multi-finger structure shown in FIG. 1;

FIG. 3 is a graph showing the transistor characteristics of the p-channel transistor shown in FIG. 2;

FIG. 4 is a schematic cross-sectional view showing the semiconductor device of FIG. 1;

FIG. 5 is a schematic layout diagram showing a semiconductor device according to a second embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view showing the semiconductor device of FIG. 5;

FIG. 7 is a graph showing the transistor characteristics of a transistor arranged in a 45-degree layout when its resistance reduction rate α is 0.95; and

FIG. 8 is a graph showing the transistor characteristics of a transistor arranged in a 45-degree layout when its resistance reduction rate α is 0.93.

Claims

1. A semiconductor device comprising: a first transistor including a plurality of first gates that are arranged in a multi-finger structure, wherein the plurality of first gates are arranged in parallel at a predetermined pitch in a first region; anda second transistor including a plurality of second gates that are arranged in a multi-finger structure and having a conductivity type differing from that of the first transistor, wherein the plurality of second gates are arranged in parallel at a predetermined pitch and at an angle of 45 degrees with respect to a gate width direction of the first transistor in a second region, with one of the plurality of second gates having a maximum gate width;wherein the second region includes an ineffective region free from the second transistor, and a ratio of the pitch between the second gates to the maximum gate width of the second transistor is set in accordance with a ratio of the area of the ineffective region to the area of the second region.

2. The semiconductor device according to claim 1, wherein the second transistor has a predetermined specific on-resistance dependent that is in accordance with the ratio of the area of the ineffective region to the area of the second region, and the ratio of the pitch between the second gates to the maximum gate width of the second transistor is set in a manner that a value of a first on-resistance obtained when each second gate of the second transistor is arranged at an angle of 45 degrees with respect to the gate width direction of the first transistor is smaller than a value of a second on-resistance obtained when each second gate of the second transistor is arranged parallel to the gate width direction of the first transistor.

3. The semiconductor device according to claim 2, wherein the ratio of the pitch between the second gates to the maximum gate width of the second transistor is calculated using a first coefficient indicating a ratio of the first on-resistance to the second on-resistance and a second coefficient indicating the ratio of the area of the ineffective region to the area of the second region.

4. The semiconductor device according to claim 1, wherein the first region and the second region each have a square shape or a rectangular shape, each first gate of the first transistor is parallel to one side of the first region, and each second gate of the second transistor is arranged at an angle of 45 degrees with respect to one side of the second region.

5. The semiconductor device according to claim 1, wherein the first and second transistors each have a channel, with the semiconductor device being manufactured using a silicon wafer including a crystal axis defining a channel direction for each of the first and second transistors and a crystal plane defining a channel formation plane for each of the first and second transistors, with the first and second transistors having different channel directions or different channel formation planes that are based on mobility of a carrier dependent on the conductivity type.

6. A semiconductor device comprising: a first transistor including a plurality of first gates that are arranged in a multi-finger structure, wherein the plurality of first gates are arranged in parallel at a predetermined pitch in a first region; anda second transistor including a plurality of second gates that are arranged in a multi-finger structure and having a conductivity type differing from that of the first transistor, wherein the plurality of second gates are arranged in parallel at a predetermined pitch and at an angle of 45 degrees with respect to a gate width direction of the first transistor in a second region, with one of the plurality of second gates having a maximum gate width;wherein the second transistor has a predetermined specific on-resistance, and a ratio of the pitch between the second gates to the maximum gate width of the second transistor is set so that a value of a first on-resistance obtained when the second gates of the second transistor are each arranged at an angle of 45 degrees with respect to the gate width direction of the first transistor is smaller than a value of a second on-resistance obtained when the second gates of the second transistor are each arranged parallel to the gate width direction of the first transistor.

7. The semiconductor device according to claim 6, wherein the first region and the second region each have a square shape or a rectangular shape, each first gate of the first transistor is parallel to one side of the first region, and each second gate of the second transistor is arranged at an angle of 45 degrees with respect to one side of the second region.

8. The semiconductor device according to claim 6, wherein the first and second transistors each have a channel, with the semiconductor device being manufactured using a silicon wafer including a crystal axis defining a channel direction for each of the first and second transistors and a crystal plane defining a channel formation plane for each of the first and second transistors, with the first and second transistors having different channel directions or different channel formation planes that are based on mobility of a carrier dependent on the conductivity type.

9. The semiconductor device according to claim 8, wherein the silicon wafer has a (100) plane main surface, on which the first and second transistors are both formed, and a (110) plane orientation flat.

10. The semiconductor device according to claim 1, wherein the pitch between the second gates is a fixed value, and the ratio of the pitch between the second gates to the maximum gate width of the second transistor is set by fixing the pitch between the second gates and changing the maximum gate width.

11. The semiconductor device according to claim 1, wherein the pitch between the second gates is a fixed value determined based on a breakdown voltage of each of the first and second transistors.

12. The semiconductor device according to claim 1, wherein the first and second transistors are each formed using an LDMOSFET.

13. The semiconductor device according to claim 1, wherein the first and second transistors each have a trench gate structure.

14. The semiconductor device according to claim 1, wherein the first transistor is a p-channel transistor, and the second transistor is an n-channel transistor.

15. The semiconductor device according to claim 1, further comprising: a control circuit including a p-channel transistor and an n-channel transistor, each having a gate and a gate width direction, with the p-channel transistor and the n-channel transistor being arranged so that their gate width directions are parallel.