For 1/2 acres lots, you'll mostly have to look at a custom builder. Other than that, as some have already suggested, Ryan Homes is probably one of the very few big builders around this area that consistently provides that kind of acreage.
Note: Although I agree that Ryan is probably one of the best builders (even against some custom builders) in this area, some of their locations can be a little questioning. We moved here a year ago and recently started looking. After falling in love with a few models by Ryan, we couldn't get comfortable with paying $300K and having a trailer park across the street. In another instance, the lots were spectacular with the rolling hills and cul-de-sac landscapes, but we realized that we were out in the middle of nowhere (Travelers Rest, if anyone is interested). I think that was the only new subdivision within 5 square miles. Oh yeah, the new Wal-Mart was just down the street. I guess you could call that a plus.
Either way, you can find what you're looking for........its just gonna take a lot of looking. This area is being bought up so fast by just about every tract builder around, that getting a 1/2ac lot will eventually mean paying out the #*$&$.
good luck...