High voltage MOSFET having Si/SiGe heterojuction structure and method of manufacturing the same
View Patent ↗Provided are high voltage metal oxide semiconductor field effect transistor (HVMOSFET) having a Si/SiGe heterojunction structure and method of manufacturing the same. In this method, a substrate on which a Si layer, a relaxed SiGe epitaxial layer, a SiGe epitaxial layer, and a Si epitaxial layer are stacked or a substrate on which a Si layer having a well region, a SiGe epitaxial layer, and a Si epitaxial layer are stacked is formed. For the device having the heterojunction structure, the number of conduction carriers through a potential well and the mobility of the carriers increase to reduce an on resistance, thus increasing saturation current. Also, an intensity of vertical electric field decreases so that a breakdown voltage can be maintained at a very high level. Further, a reduction in vertical electric field due to the heterojunction structure leads to a gain in transconductance (Gm), with the results that a hot electron effect is inhibited and the reliability of the device is enhanced.
1. A high voltage metal oxide semiconductor field effect transistor, comprising:
a base substrate comprising:
a Si substrate;
a relaxed SiGe epitaxial layer formed on at least a portion of the Si substrate;
a SiGe epitaxial layer formed on at least a portion of the relaxed SiGe epitaxial layer; and
a Si epitaxial layer formed on at least a portion of the SiGe epitaxial layer;
a gate insulating layer formed on at least a portion of the base substrate
a gate formed over the base substrate and electrically isolated from the base substrate by the gate insulating layer;
a source region formed at least in a first portion on or in the SiGe epitaxial layer near the gate;
a drift region formed in a second portion of the SiGe epitaxial layer near the gate; and
a drain region formed in a predetermined portion of the drift region.
2. The transistor according to claim 1 , wherein the relaxed SiGe epitaxial layer is formed of relaxed Si (1→X) Ge (0→1-X) , such that a Ge content by weight is gradually increased from 0% to any in the range of 10% to 20% by gradually varying x from 100% to any in the range of 80 to 90%.
3. The transistor according to claim 1 , wherein the SiGe epitaxial layer has a greater thickness than a diffused thickness of the drift region.
4. The transistor according to claim 1 , wherein the Si epitaxial layer has a thickness of about 4 to 20 nm.
5. The transistor according to claim 1 , wherein the gate partially overlaps the drift region.
6. The transistor according to claim 1 , wherein the source region has a lightly doped drain (LDD) structure.
7. The transistor according to claim further comprising a source contact region disposed on one side of the source region.
8. A high voltage metal oxide semiconductor field effect transistor, comprising:
a base substrate comprising:
a Si substrate
a well region formed on at least a portion of the Si substrate;
a SiGe epitaxial layer formed on at least a portion of the well region;
a Si epitaxial layer formed on at least a portion of the SiGe epitaxial layer;
a gate insulating layer formed on at least a portion of the base substrate
a gate formed above the base substrate and electrically isolated from the base substrate by the gate insulating layer;
a source region formed at least in a first portion on or in the well region near the gate;
a drift region formed at least in a second portion on or in the well region near the gate; and
a drain region formed in a predetermined portion of the drift region.
9. The transistor according to claim 8 , wherein the SiGe epitaxial layer has a greater thickness than a diffused thickness of the drift region.
10. The transistor according to claim 8 , wherein the Si epitaxial layer has a thickness of about 4 to 20 nm.
11. The transistor according to claim 8 , wherein the gate partially overlaps the drift region.
12. The transistor according to claim 8 , wherein the source region has a lightly doped drain (LDD) structure.
13. The transistor according to claim 8 , further comprising a source contact region disposed on one side of the source region.