Semiconductor device and manufacturing method of the same
Provided is a technology capable of suppressing a reduction in electron mobility in a channel region formed in a strained silicon layer. A p type strained silicon layer is formed over a p type silicon-germanium layer formed over a semiconductor substrate. The p type strained layer has a thickness adjusted to be thicker than the critical film thickness at which no misfit dislocation occurs. Accordingly, misfit dislocations occur in the vicinity of the interface between the p type strained silicon layer and p type silicon-germanium layer. At a position which is below the end of a gate electrode and at which misfit dislocations occur, the impurity concentration of the n type strained silicon layer and n type silicon-germanium layer is 1×10 19 cm −3 or less.
1. A semiconductor device including an MISFET, comprising:
(a) a silicon-germanium layer formed over a semiconductor substrate;
(b) a strained silicon layer formed over the silicon-germanium layer;
(c) a gate insulating film formed over the strained silicon layer;
(d) a gate electrode formed over the gate insulating film; and
(e) a source region and a drain region;
wherein the strained silicon layer is thicker than a critical film thickness at which misfit dislocations occur and the misfit dislocations exist on an interface between the strained silicon layer and silicon-germanium layer,
wherein the source region is formed in the strained silicon layer but not formed in the silicon-germanium layer, and the drain region is formed in both the strained silicon layer and the silicon-germanium layer so that said source region and said drain region are not symmetric.
2. A semiconductor device according to claim 1 ,
wherein the source region and the drain region are n − type regions, respectively, and
wherein a channel region formed between the source region and the drain region is a p − type region.
3. A semiconductor device according to claim 1 ,
wherein the MISFET is a LDMISFET, and
wherein the drain region is comprised of an impurity diffusion region and a drain offset region having a lower impurity concentration than the impurity diffusion region.
4. A semiconductor device according to claim 3 ,
wherein the source region, the impurity diffusion region and the drain offset region are n − type regions, respectively, and
wherein a channel region formed between the source region and the drain offset region is a p − type region.
5. A semiconductor device according to claim 1 , wherein the source region is formed to have a depth from an upper surface of said strained silicon layer that is less than the critical film thickness at which misfit dislocations occur and said drain region is formed to have a depth from the upper surface of said strained silicon layer which is greater than the critical film thickness at which misfit dislocations occur so that said source region is formed in said strained silicon layer to be entirely above the area where the misfit dislocations occur and the drain region is formed so that a portion of said drain region extends into the area where the misfit dislocations occur.
6. A semiconductor device including an MISFET, comprising:
a silicon-germanium layer formed over a semiconductor substrate;
a strained silicon layer formed over the silicon-germanium layer;
a gate insulating film formed over the strained silicon layer;
a gate electrode formed over the gate insulating film;
a source region; and
a drain region,
wherein the source region is formed in the strained silicon layer but not formed in the silicon-germanium layer, and the drain region is formed in both the strained silicon layer and the silicon-germanium layer so that said source region and said drain region are not symmetric.
7. A semiconductor device according to claim 6 ,
wherein the source region and the drain region are n − type regions, respectively, and
wherein a channel region formed between the source region and the drain region is a p − type region.
8. A semiconductor device according to claim 6 ,
wherein the MISFET is a LDMISFET, and
wherein the drain region is comprised of an impurity diffusion region and a drain offset region having a lower impurity concentration than the impurity diffusion region.
9. A semiconductor device according to claim 8 ,
wherein the source region, the impurity diffusion region and the drain offset region are n − type regions, respectively, and
wherein a channel region formed between the source region and the drain offset region is a p − type region.