More problems in this area are asked in recent years. The problems that appear in GATE are more on basics of the MOSFET device. Some important relations which are related to device concepts are also important. Try to understand the applicability of the related equations and their limitations. Since the topic is relatively recent, but good books are available. You can refer to the books given in the list of books for GATE EC.
GATE, with 1 Comment
This set consists of GATE problems of 2 Marks each. Problems of GATE 2016 are also included.