Semi-trucks can typically be shipped like most any other big vehicle. However, because of their size, they will not be able to be shipped on open or enclosed transportation services. Therefore, they will either need to be towed or, more likely, be moved on a flatbed or a lowboy truck.
Flatbed and lowboy trucks are designed to haul larger vehicles that cannot fit on standard transport trucks like open or enclosed trailers. You'll need the dimensions of the semi-truck when you get a quote to ship it. Please note as well that no shipper can move any trailers along with a semi-truck.