FinFET with shorter fin height in drain region than source region and related method
A FinFET includes a semiconductor fin, and a source region and a drain region in the same semiconductor fin. The drain region has a first fin height above a trench isolation; and the source region has a second fin height above the trench isolation. The first fin height is less than the second fin height. The FinFET may be used, for example, in a scaled laterally diffused metal-oxide semiconductor (LDMOS) application, and exhibits reduced parasitic capacitance for improved radio frequency (RF) performance. A drain extension region may have the first fin height, and a channel region may have the second fin height. A method of making the FinFET is also disclosed.
1. A fin-type field effect transistor (FinFET), comprising:
a semiconductor fin having a trench isolation adjacent thereto;
a drain region in the semiconductor fin, the drain region having a first fin height above the trench isolation;
a source region in the same semiconductor fin as the drain region, the source region having a second fin height above the trench isolation,
wherein the first fin height is less than the second fin height; and
a gate extending across the semiconductor fin.
2. The FinFET of claim 1 , wherein the first fin height is between 40% and 60% of the second fin height.
3. The FinFET of claim 1 , wherein the drain region is adjacent to a drain extension region in an n-well in the semiconductor fin, wherein the drain extension region has the first fin height.
4. The FinFET of claim 3 , further comprising a channel region under the gate in the semiconductor fin and between the source region and the drain extension region, wherein the channel region has the second fin height.
5. The FinFET of claim 4 , wherein the channel region is positioned in a p-well in the semiconductor fin, and wherein a transition between the first fin height and the second fin height is positioned in a gap between the p-well and the n-well in the semiconductor fin.
6. The FinFET of claim 1 , wherein the source region includes a source region epitaxial portion above the trench isolation, and the drain region includes a drain region epitaxial portion above the trench isolation, wherein the source region epitaxial region is wider than the drain region epitaxial portion.
7. The FinFET of claim 6 , wherein the drain region includes another drain region epitaxial portion extending below an upper surface of the trench isolation.
8. The FinFET of claim 1 , wherein the trench isolation has a first isolation height relative to a bottom of the semiconductor fin adjacent the drain region in the semiconductor fin and a second isolation height relative to the bottom of the semiconductor fin adjacent the source region in the semiconductor fin, wherein the first isolation height is greater than the second isolation height, defining a step in the trench isolation adjacent the semiconductor fin.
9. The FinFET of claim 8 , wherein the gate extends over the step in the trench isolation adjacent the semiconductor fin.