A method of forming a portion (10) of a compound semiconductor MOSFET structure comprises forming a compound semiconductor layer structure (14) and an oxide layer (20) overlying the same. Forming the compound semiconductor structure (14) includes forming at least one channel material (16) and a group-III rich surface termination layer (18) overlying the at least one channel material. Forming the oxide layer (20) includes forming the oxide layer to overlie the group-III rich surface termination layer and comprises one of (a) depositing essentially congruently evaporating oxide of at least one of (a(i)) a ternary oxide and (a(ii)) an oxide more complex than a ternary oxide and (b) depositing oxide molecules, with use of at least one of (b(i)) a ternary oxide and (b(ii)) an oxide more complex than a ternary oxide.