Method of producing a t-shaped gate electrode

Claim 2

A production method for a semiconductor device having a T-shaped gate electrode disposed in a two stage recess and having a head comprising: forming an active layer on a semiconductor substrate; producing a broad recess in said active layer of said semiconductor substrate, leaving a dummy gate in said active layer; covering said dummy gate and forming a pattern for producing a head portion of a T-shaped gate electrode opposite said dummy gate; exposing said dummy gate utilizing said pattern; then producing a narrow recess within the broad recess offset from the center of the broad recess, thereby producing a two stage recess; and producing a T-shaped gate electrode in the narrow recess and producing the head of the T-shaped gate electrode using the pattern.

Claim 3

The production method of claim 1 comprising: producing the broad recess by depositing a first nitride film on said active layer of said semiconductor substrate and etching said first nitride film and said active layer using a first resist pattern as a mask, thereby producing a first gate/source recess of width W GS ', a first gate/drain recess of width W GD ', and a first dummy gate of width W G ', where W GS '<W GD ' and the sum of W GS ', W G ', and W GD ' equals W, the width of the broad recess; removing the first resist pattern and the first nitride film; covering said dummy gate and forming a pattern by depositing a second nitride film on the substrate burying the dummy gate, the gate/source recess, and the gate/drain recess and producing a second resist pattern having an aperture for the head of the T-shaped gate electrode on said second nitride film; exposing said dummy gate by etching said second nitride film using said second resist pattern as a mask and producing the narrow recess having a width W G by etching said active layer using said second resist pattern and said second nitride film as a mask, thereby producing a second gate/source recess of width W GS and a second gate/drain recess of width W GD , where the sum of W G , W GD , and W GS equals W; and said T-shaped gate electrode is produced by depositing gate electrode metal and removing said second resist pattern and said gate electrode metal disposed thereon by lift-off and thereafter removing said second nitride film to produce the T-shaped gate electrode in the narrow recess.

Claim 4

The production method of claim 2, wherein the ratios of W GS ' to W GD ' and W GS to W GD are 1:2.