double diffused drain
I hope that this answers your questions fairly...
1.LDD is Lightly Doped drain. If a MOSFET has a LDD structure, the built in potential, Vbi in a LDD-MOSFET will be smaller as compared to conventional MOSFET’s; therefore thethreshold voltage reduction due to the short channel effect will be smaller
2.I do not know what DDD is.
3.LDMOS is laterally diffused MOSFET. It is used in HF,RF applications. In the LDMOS the source is formed near the body on the p -sub isolated by epitaxial layer. The advantage for this configuration is that, there is no gain reduction and the performance is bettered.