Transistor and formation method thereof

Abstract

The invention provides a transistor and a formation method thereof. The formation method of the transistor comprises the steps that a substrate comprising a first region and a second region is provided; a dielectric layer is formed on the surface of the substrate, the dielectric layer of the first region is internally provided with a first opening, and the dielectric layer of the second region is internally provided with a second opening; a gate dielectric layer is formed on the surface of the dielectric layer, the side wall and the bottom surface of the first opening and the side wall and the bottom surface of the second opening; a cover layer is formed on the surface of the gate dielectric layer, wherein the material of the cover layer is first type of work function material; a first work function layer is formed on the surface of the cover layer of the first region, wherein the material of the first work function layer is the first type of work function material; a second work function layer is formed on the surface of the first work function layer and the surface of the cover layer of the second region, wherein the material of the second work function layer is second type of work function material; and a gate layer fully filling the first opening and the second opening is formed on the surface of the second work function layer. The mismatch problem between a PMOS transistor and an NMOS transistor can be improved.

Description

technical field [0001] The invention relates to the technical field of semiconductor manufacturing, in particular to a transistor and a forming method thereof. Background technique [0002] Static Random Access Memory (SRAM), as a member of memory, has the advantages of high speed, low power consumption and compatibility with standard processes, and is widely used in computers, personal communications, consumer electronics (smart cards, digital cameras, Multimedia player) and other fields. [0003] The storage unit of the SRAM includes a 4T (transistor) structure and a 6T (transistor) structure. For a 6T SRAM size unit, it includes: a first PMOS transistor P1 , a second PMOS transistor P2 , a first NMOS transistor N1 , a second NMOS transistor N2 , a third NMOS transistor N3 and a fourth NMOS transistor N4 . Wherein, the P1 and P2 are pull-up transistors; the N1 and N2 are pull-down transistors; and the N3 and N4 are transfer transistors. [0004] In the prior art, in ord...

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Problems solved by technology

[0006] However, due to the difference in work function layer materials required for PMOS transistors and NMOS transistors, the performance of the formed SRAM is unstable.

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