For a better insight into the mind-boggling integration that has been done for cellphones over these last two decades, have a look at a recent teardown of a Samsung Galaxy S7 here:
https://www.ifixit.com/Teardown/Samsung+Galaxy+S7+Teardown/56686
Its not easy to tell which ICs do RF things and which don't, so its a good thing the teardown author identifies most of the big stuff for you. In it you will find that there are multiple RF devices, all ICs, with a lot going on inside. They include things like multiple receivers, multiple bands, full duplex operation (rx and tx at the same time), complex modulators (ie. with PA envelope tracking), automatic adaptive antenna tuners and so on. Here is some example info on some of the RF ICs:
https://www.qorvo.com/rf-fusion
https://www.qualcomm.com/news/relea...s-fourth-generation-3glte-multimode-modem-and
and as impressive as these are, they are not state-of-the art. The latest stuff being designed into cellphones right now are always secret, where technical details are not available to anyone except hand picked customers, usually cellphone manufacturers. The last time I saw a block diagram of the insides or a cellphone transceiver IC chipset (ie. two or three parts), I was amazed at how many processor cores there were, or how many RF receivers and transmitters there were, or how many bands they can handle in one chip. And that was about 6 years ago. Transmitters in portable/mobile phones have not used discrete devices for the RF chain since they were invented, I think. Well perhaps the first few models had some discrete amplifiers, but probably not past the DynaTac 8000x portable phone, introduced in 1984. One example that is interesting was the Motorola Startac phone, a revolutionary design back in its day (1996). Even back then, pretty much all the active RF stuff is in IC form, but it has some discrete filters that you won't find in phones so much these days.