# US 2014/0191285 A1 · Semiconductor device having epitaxial structures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191285 A1 - Document ID: US20140191285A1 - Status: Published application - Kind: A1 - Application number: 14/203,581 - Filed: 2014-03-11 - Published: 2014-07-10 - Earliest claimed: 2011-07-25 - Assignees: United Microelectronics Corp. - Applicants: United Microelectronics Corp. - Inventors: Chin-I Liao; Teng-Chun Hsuan; I-Ming Lai; Chin-Cheng Chien - Web page: https://patentgrep.com/patent/US20140191285A1 ## CPC - H10D 62/822: comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions - H10D 30/0275: {forming single crystalline semiconductor source or drain regions resulting in recessed gates, e.g. forming raised source or drain regions} - H10D 30/797: {being in source or drain regions, e.g. SiGe source or drain} - H10D 62/021: {Forming source or drain recesses by etching e.g. recessing by etching and then refilling} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A semiconductor device having epitaxial structures includes a gate structure positioned on a substrate, epitaxial structures formed in the substrate at two sides of the gate structure, and an undoped cap layer formed on the epitaxial structures. The epitaxial structures include a dopant. The epitaxial structures and the undoped cap layer include a first semiconductor material having a first lattice constant and a second semiconductor material having a second lattice constant. The second lattice constant is larger than the first lattice constant. The second semiconductor material in the epitaxial structure includes a first concentration and the second semiconductor material in the undoped cap layer includes a second concentration. The second concentration is lower than the first concentration, and is upwardly decreased. ## Claims ### Claim 1 A semiconductor device having epitaxial structures comprising: a gate structure positioned on a substrate; epitaxial structures formed in the substrate at two sides of the gate structure, the epitaxial structure comprising a dopant, a first semiconductor material having a first lattice constant, and a second semiconductor material having a second lattice constant, the second lattice constant being larger than the first lattice constant, and the second semiconductor material in the epitaxial structure having a first concentration; and an undoped cap layer formed on the epitaxial structures, the undoped cap layer comprising the first semiconductor material and the second semiconductor material, the second semiconductor material in the undoped cap layer having a second concentration, wherein the second concentration is lower than the first concentration and upwardly decreased. ### Claim 2 (depends on 1) The semiconductor device having epitaxial structures according to claim 1, further comprising: lightly-doped drains (LDDs) formed in the substrate respectively at the two sides of the gate structure; and a spacer formed on sidewalls of the gate structure. ### Claim 3 (depends on 1) The semiconductor device having epitaxial structures according to claim 1, wherein the first semiconductor material comprises silicon (Si) and the second semiconductor material comprises germanium (Ge). ### Claim 4 (depends on 1) The semiconductor device having epitaxial structures according to claim 1, wherein the second concentration is about 25%. ### Claim 5 (depends on 4) The semiconductor device having epitaxial structures according to claim 4, wherein the second concentration is upwardly decreased to 0%. ### Claim 6 (depends on 1) The semiconductor device having epitaxial structures according to claim 1, further comprising an undoped under layer positioned between the epitaxial structure and the substrate, the undoped under layer comprises the first semiconductor material and the second semiconductor material. ### Claim 7 (depends on 6) The semiconductor device having epitaxial structures according to claim 6, wherein a concentration of the second semiconductor material in the undoped under layer is between 10% and 25%. ### Claim 8 (depends on 7) The semiconductor device having epitaxial structures according to claim 7, wherein the concentration of the second semiconductor material in the undoped under layer is upwardly increased. ### Claim 9 A semiconductor device having epitaxial structures comprising: a gate structure positioned on a substrate; epitaxial structures formed in the substrate at two sides of the gate structure, the epitaxial structure comprising a dopant, a first semiconductor material having a first lattice constant, and a second semiconductor material having a second lattice constant, the second lattice constant being larger than the first lattice constant, and the second semiconductor material in the epitaxial structure having a first concentration; a first undoped cap layer formed on the epitaxial structures, the first undoped cap layer comprising the first semiconductor material and the second semiconductor material, the second semiconductor material in the first undoped cap layer having a second concentration, wherein the second concentration is lower than the first concentration and upwardly decreased; and a second undoped cap layer formed on the first undoped cap layer, the second undoped cap layer comprising the first semiconductor material and the second semiconductor material, the second semiconductor material in the second undoped layer having a third concentration, and the third concentration is equal to 0%. ### Claim 10 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, further comprising: lightly-doped drains (LDDs) formed in the substrate respectively at the two sides of the gate structure; and a spacer formed on sidewalls of the gate structure. ### Claim 11 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, wherein the first semiconductor material comprises silicon (Si) and the second semiconductor material comprises germanium (Ge). ### Claim 12 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, wherein the second concentration is about 25%. ### Claim 13 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, wherein a thickness of the first undoped cap layer and a thickness of the second undoped cap layer have a ratio, and the ratio is about 1:2. ### Claim 14 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, further comprising a third undoped cap layer formed between the first undoped cap layer and the second undoped cap layer, the second semiconductor material in the third undoped cap layer has a fourth concentration, and the fourth concentration is between the second concentration and the third concentration. ### Claim 15 (depends on 14) The semiconductor device having epitaxial structures according to claim 14, wherein the fourth concentration is about 10%. ### Claim 16 (depends on 15) The semiconductor device having epitaxial structures according to claim 15, wherein a thickness of the first undoped cap layer, a thickness of the second undoped cap layer, and a thickness of the third undoped cap layer have a ratio, and the ratio is about 1:1:1. ### Claim 17 (depends on 9) The semiconductor device having epitaxial structures according to claim 9, further comprising an undoped under layer positioned between the epitaxial structure and the substrate, the undoped under layer comprises the first semiconductor material and the second semiconductor material. ### Claim 18 (depends on 17) The semiconductor device having epitaxial structures according to claim 17, wherein a concentration of the second semiconductor material in the undoped under layer is between 10% and 25%. ### Claim 19 (depends on 18) The semiconductor device having epitaxial structures according to claim 18, wherein a concentration of the second semiconductor material in the undoped under layer is upwardly increased.