Mobility enhancement by strained channel CMOSFET with single workfunction metal-gate and fabrication method thereof

Abstract

The present invention provides a complementary metal-oxide-semiconductor (CMOS) device and a fabrication method thereof. The CMOSFET device includes a compressively strained SiGe channel for a PMOSFET, as well as a tensile strained Si channel for an NMOSFET, thereby enhancing hole and electron mobility for the PMOSFET and the NMOSFET, respectively. As such, the threshold voltages of the two types of transistors can be obtained in oppositely symmetric by single metal gate.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to complementary metal-oxide-semiconductor (CMOS) technology. More particularly, it relates to combining a compressively strained SiGe channel of a PMOSFET with a local tensile strained Si channel of an NMOSFET, such that a band gap narrowing of the CMOSFET and improving holes and electrons mobility of the PMOSFET and NMOSFET, respectively. [0003] 2. Description of the Related Art [0004] The density of integrated circuits (IC) continues to increase and feature size thereof continues to scale down, improving the performance of IC devices and lowering manufacturing costs. Shorter channel length causes gate electrodes to lose channel controllability due to the short channel effect (SCE). This controllability problem can be solved by reducing the thickness of the gate dielectric layer (silicon dioxide), and this decreases the operating voltage and increases driving current. As a result, the...

AI Technical Summary

Benefits of technology

[0012] According to the invention, a method and a device for mobility enhancement by strained channel CMOSFET with single workfunction metal-gate are provided; wherein a PMOSFET channel is compressively strained for improving hole mobility, and an NMOSFET channel is tensile strain for enhancing electron mobility.

[0013] An exemplary embodiment of the present invention uses a compressively strained channel, for narrowing the band gap.

[0016] The present invention combines a PMOSFET compressively strained channel and an NMOSFET tensile strained channel. The compressively strained channel enhances the PMOSFET hole mobility, and the tensile stress enhances the NMOSFET electron mobility.

Problems solved by technology

As a result, the leakage current is significantly increased with a direct tunneling effect, and the controllability issue still exists.

When IC dimensions decrease, the poly-Si has issues of poly depletion and sheet resistance.

The former, however, is a complex process, and the latter is limited by solid solubility.

However, the tensile strained Si cannot significantly improve the hole mobility in PMOSFET.

This method requires a SiGe virtual substrate that leads increasing costs and the thickness of the ultra-thin Si cap layer overlying the PMOSFET is difficult to control.

Disadvantages of the global strain include high cost, low hole mobility, and high defect density in the SiGe virtue substrate.

The disadvantage of the local strain is difficult in process control.

A compressively strained SiGe channel is used for enhancing the hole mobility of the PMOSFET, but the electron mobility of the NMOSFET is not improved.

Images