EP0057558A2
Expired / Lapsed
EP
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Field effect semiconductor device and method of manufacturing such a device
Assignee: Fujitsu Ltd
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Filing: 1982-01-26
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Granted: —
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Expires: 2002-01-26
Abstract
Abstract A field effect semiconductor device has a substrate (11) of a compound semiconductor in which an active region (15) is formed. A gate electrode (16) is formed on the active region. The gate electrode (16) comprises silicon and at least one refractory metal, but the composition of the gate electrode (16) varies through its thickness. For example, the gate electrode (16) is formed from a double layer (16A, 16B) structure in which the lower layer (16A) has a higher etching rate than the upper layer (16B). After etching, the portion of the gate electrode (16) which contacts the active region (15) is shorter than the portion of the gate electrode (16) remote from the active region (15). Thus a gate length of less than 1 micrometer can be provided.Alternatives to the double layer (16A, 16B) structure for providing gate electrode (16) can be used. In each alternative, composition of the gate electrode (16) varies through its thickness so that different levels of the gate electrode (16) are subject to different etching rates.Methods of manufacturing such a field effect semiconductor device are described.
Inventors
- 👤 Masumi Fukuta
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 19:45
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/061; H10D30/0612; H10D30/0616; H10D30/60; H10D30/67; H10D30/6729; H10D30/6737; H10D30/6738; H10D30/674; H10D30/675; H10D30/80; H10D64/00; H10D64/01; H10D64/012; H10D64/0124; H10D64/0125; H10D64/20; H10D64/27; H10D64/311; H10D64/411; H10D64/60; H10D64/64; H10P; H10P50/00; H10P50/20; H10P50/26; H10P50/264; H10P50/266; H10P50/267; H10P50/268; H10D62/00; H10D62/80; H10D62/85
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
76 words
A field effect semiconductor device comprising:- a substrate of a compound semiconductor, having an active region therein, and a gate electrode, on the active region, comprising silicon and at least one refractory metal, wherein the composition of the gate electrode varies through its thickness, and the length of a portion of the gate electrode which contacts the active region is shorter than the length of a portion of the gate electrode remote from the active region.
Claim 2
Dependent Claim
76 words
A field effect semiconductor device comprising:- a substrate of a compound semiconductor, having an active region therein, and a gate electrode, on the active region, comprising silicon and at least one refractory metal, wherein the composition of the gate electrode varies through its thickness, and the length of a portion of the gate electrode which contacts the active region is shorter than the length of a portion of the gate electrode remote from the active region.
Claim 3
Dependent Claim
42 words
A device as claimed in claim 1, wherein the gate electrode comprises a layer constituted of silicon and at least one refractory metal, the proportions in which those substances are present in the layer gradually varying through the thickness of the layer.
Claim 4
Dependent Claim
32 words
A device as claimed in claim 1, wherein the gate electrode comprises a plurality of layers each constituted of silicon and at least one refractory metal, different layers having respective different compositions.
Claim 5
Independent Claim
24 words
A device as claimed in any preceding claim, wherein the said at least one refractory metal is W or Ti or Mo or Ta.
Claim 6
Independent Claim
51 words
A device as claimed in any preceding claim, wherein the composition of the gate electrode varies through its thickness so that the portion of the gate electrode which contacts the active region has a higher etching rate than that of the portion of the gate electrode remote from the active region.
Claim 7
Independent Claim
24 words
A device as claimed in any preceding claim, wherein the gate electrode is covered by a material of high conductivity, for example Au-Ge alloy.
Claim 8
Independent Claim
24 words
A device as claimed in any preceding claim, having source and drain electrodes to the sides of the gate electrode on the active region.
Claim 9
Independent Claim
13 words
A device as claimed in any preceding claim, being a Schottky gate device.
Claim 10
Dependent Claim
100 words
Method of manufacturing a field effect semi- conductor device, comprising :- forming an active region in a compound semi- conductor substrate, and forming a layer structure , on the active region, comprising silicon and at least one refractory metal, wherein the layer structure is so formed that its composition varies through its thickness to provide a portion of the layer structure which contacts the active region with a higher etching rate than that of a portion of the layer structure remote from the active region, and wherein the method further comprises etching the layer structure to provide a gate electrode.
Claim 11
Dependent Claim
100 words
Method of manufacturing a field effect semi- conductor device, comprising :- forming an active region in a compound semi- conductor substrate, and forming a layer structure , on the active region, comprising silicon and at least one refractory metal, wherein the layer structure is so formed that its composition varies through its thickness to provide a portion of the layer structure which contacts the active region with a higher etching rate than that of a portion of the layer structure remote from the active region, and wherein the method further comprises etching the layer structure to provide a gate electrode.
Claim 12
Dependent Claim
47 words
A method as claimed in claim 9, wherein the layer structure is so formed as to comprise a layer constituted of silicon and at least one refractory metal, the proportions in which those substances are present in the layer gradually varying through the thickness of the layer.
Claim 13
Dependent Claim
37 words
A method as claimed in claim 9, wherein the layer structure is so formed as to comprise a plurality of layers each constituted of silicon and at least one refractory metal, different layers having respective different compositions.
Claim 14
Dependent Claim
30 words
A method as claimed in claim 9, 10 or 11, further comprising, after etching to provide the gate electrode , forming source and drain regions by an ion implantation process.
Claim 15
Dependent Claim
21 words
A method as claimed in claim 12, further comprising forming a layer of material of high conductivity on the gate electrode.
References Cited (Backward Citations)
No citation records indexed.
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