semi custom design flow
Hi Vamsi,
You can refer ASIC for Full Custom design and FPGA for Semi-Custom design flows. The reason is in ASIC you have the flexibility to design your own design blocks with libraries (eventhough Vendor provided libraries you have the option to choose). This flexibility you cant get in the Semi-Custom flows like FPGA and Semi-Custom FPGA (Altera is an example). Try google for the ASIC flow and FPGA flow differerence to get more info.
-Paul