Semiconductor device having T-shaped gate electrode

• US 6,075,262 A
• Filed: 07/25/1997
• Issued: 06/13/2000
• Est. Priority Date: 09/21/1995
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Moriuchi, Toshiaki, Yokoyama, Teruo
• Primary Examiner(s): Abraham, Fetsum
• Application Number:
  US08/900,874
• Time in Patent Office: 1,054 Days
• Field of Search: 257/94-97, 257/267, 257/280-284, 257/449, 257/454-457, 257/471-473
• US Class Current: 257/280
• CPC Class Codes: H01L 21/28587 characterised by the sectional shape, e.g. T, inverted T
• CPC Class Codes: H01L 29/42316 for field-effect transistors
• CPC Class Codes: H01L 29/66878 Processes wherein the final gate is made before the formation, e.g. activation anneal, of the source and drain regions in the active layer
• CPC Class Codes: H01L 29/7787 with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET
• CPC Class Codes: H01L 29/812 with a Schottky gate H01L29/7725, H01L29/775, H01L29/778, H01L29/806 take precedence; with Schottky contact on top of heterojunction gate H01L29/802

Abstract

A compound semiconductor transistor has a structure in which a first insulating film is formed only under a overhang of a gate electrode an upper part of which is formed widely, and a second insulating film for threshold voltage adjustment is formed on the side of a gate electrode and the first insulating film.

Claims

1. A semiconductor device comprising:

a gate electrode which is formed on a compound semiconductor layer in an Schotkky-junction and which has an overhang at an upper part of which is formed wider than a lower part;

a first insulating film selectively formed under said overhang of said gate electrode and directly contacting sidesurfaces of said lower part of the gate electrode;

a second insulating film in contact with side surfaces of said first insulating film and side surfaces of said overhang of the gate electrode; and

a source electrode and a drain electrode formed in ohmic contact with portions to be served as a source region and a drain region of said compound semiconductor layer.

2. The semiconductor device according to claim 1 wherein said first insulating film is composed of multiple layers.

3. The semiconductor device according to claim 1 wherein a second undoped compound semiconductor layer is formed under said compound semiconductor layer.

4. The semiconductor device according to claim 1 wherein said first insulating film extends like a taper from said overhang toward said compound semiconductor layer.

5. The semiconductor device according to claim 1 wherein a third insulating film is formed between said compound semiconductor layer and said second insulating film.