Lateral undercut of metal gate in SOI device

A method for making a semiconductor device, comprising:

• forming a gate dielectric on a second semiconductor layer on an insulator layer that is on a first semiconductor layer;
• forming a metal gate electrode on the gate dielectric, the metal gate electrode having a first side and a second side;
• removing portions of the metal gate electrode on the first side and the second side to form lateral undercuts with a depth;
• forming source/drain regions of the second semiconductor layer on the first and second side of the metal gate electrode, the source/drain regions having extensions a distance beneath the metal gate electrode;
• and
• wherein the depth of the lateral undercuts are at least about one-fourth the distance of the source/drain region extensions.