No. Routers route using the logical addressing afforded by IP. This is at a higher level than the physical addressing that underlies switches.
To be sure, there are routers that switch and switches that route, to one extent or another.
However, when you say, "... speed up routing in a LAN," you may not mean routing per se. You may simply need a good switch as your traffic problems seem to be internal, not WAN problems, right?
A switch inside the router makes sense generally. The switch ports can feed workgroup hubs.
Yours,
Mike