Method of forming semiconductor device

• US 8,647,941 B2
• Filed: 08/17/2011
• Issued: 02/11/2014
• Est. Priority Date: 08/17/2011
• Status: Active Grant

• Current Assignee: United Microelectronics Corporation
• Original Assignee: United Microelectronics Corporation
• Inventors: Chien, Chin-Cheng, Wu, Chun-Yuan, Liu, Chih-Chien, Lin, Chin-Fu, Tsai, Teng-Chun
• Primary Examiner(s): STARK, JARRETT J
• Application Number:
  US13/211,319
• Publication Number:
  US 20130045579A1
• Time in Patent Office: 909 Days
• Field of Search: 438/196, 438/218, 438/212, 438/938, 438/301, 438/303, 438/285, 438/299, 257/192, 257/347, 257/E21.207, 257/E21.411, 257/E21.461
• US Class Current: 438/222
• CPC Class Codes: H01L 21/76283 Lateral isolation by refilling of trenches with dielectric material
• CPC Class Codes: H01L 29/1054 with a variation of the composition, e.g. channel with strained layer for increasing the mobility
• CPC Class Codes: H01L 29/66651 with a single crystalline channel formed on the silicon substrate after insulating device isolation
• CPC Class Codes: H01L 29/78 with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence
• CPC Class Codes: H01L 29/7846 the means being located in the lateral device isolation region, e.g. STI

Abstract

A method of forming a semiconductor device includes the following steps. A semiconductor substrate having a first strained silicon layer is provided. Then, an insulating region such as a shallow trench isolation (STI) is formed, where a depth of the insulating region is substantially larger than a depth of the first strained silicon layer. Subsequently, the first strained silicon layer is removed, and a second strained silicon layer is formed to substitute the first strained silicon layer.

Claims

1. A method for forming a semiconductor device, comprising:

providing a semiconductor substrate comprising a first strained silicon layer;

forming at least an insulating region, wherein a depth of the insulating region is substantially larger than a depth of the first strained silicon layer;

removing the first strained silicon layer; and

forming a second strained silicon layer.

2. The method for forming a semiconductor device according to claim 1, wherein the insulating region comprises a shallow trench isolation (STI).

3. The method for forming a semiconductor device according to claim 2, wherein the method for forming the shallow trench isolation comprises:

forming a patterned mask on the semiconductor substrate;

performing an etching process for forming at least a trench;

performing a thermal oxidation process for forming an oxide layer covering a bottom and inner sides of the trench;

forming a dielectric layer made of oxide for filling the trench; and

performing a chemical mechanical polishing (CMP) process.

4. The method for forming a semiconductor device according to claim 1, wherein the semiconductor substrate comprises a first epitaxial layer and a second epitaxial layer disposed between the semiconductor substrate and the first strained silicon layer, the second epitaxial layer is disposed on the first epitaxial layer, and a depth of the second epitaxial layer is substantially larger than the depth of the insulating region.

5. The method for forming a semiconductor device according to claim 4, wherein a portion of the second epitaxial layer is removed, as the first strained silicon layer is removed.

6. The method for forming a semiconductor device according to claim 5, wherein the left second epitaxial layer surrounds a bottom of the insulating region.

7. The method for forming a semiconductor device according to claim 5, wherein after removing a portion of the second epitaxial layer, and before forming the second strained silicon layer, a third epitaxial layer is formed on the left second epitaxial layer.

8. The method for forming a semiconductor device according to claim 7, wherein the first epitaxial layer, the second epitaxial layer and the third epitaxial layer respectively comprise a silicon-germanium epitaxial layer.

9. The method for forming a semiconductor device according to claim 8, wherein a material of silicon-germanium epitaxial layer is denoted as (Si_(1-y)Ge_y).

10. The method for forming a semiconductor device according to claim 9, wherein a mole fraction (y) of germanium in the first epitaxial layer increases progressively from an interface between the semiconductor substrate and the first epitaxial layer towards an interface between the first epitaxial layer and the second epitaxial layer.

11. The method for forming a semiconductor device according to claim 10, wherein a mole fraction (y) of germanium in the second epitaxial layer and a mole fraction (y) of germanium in the third epitaxial layer are substantially fixed and equal to the mole fraction (y) of germanium at the interface between the first epitaxial layer and the second epitaxial layer.

12. The method for forming a semiconductor device according to claim 1, further comprising:

defining at least an active region in the semiconductor substrate, wherein the insulating region surrounds the active region;

forming at least a first well having a first conductive type in the active region;

forming at least a gate structure on the first well; and

forming at least a source/drain region having a second conductive type in the semiconductor substrate at two sides of the gate structure.

13. The method for forming a semiconductor device according to claim 12, wherein the first conductive type comprises n-type or p-type, the second conductive type comprises p-type or n-type, and the first conductive type is different from the second conductive type.

14. The method for forming a semiconductor device according to claim 12, wherein the gate structure comprises a gate dielectric layer, a gate conductive layer, a cap layer and a spacer.

15. The method for forming a semiconductor device according to claim 14, wherein the gate dielectric layer comprises a low-k (low dielectric constant) gate dielectric layer or a high-k gate dielectric layer.