Can only men could obtain a superego?
No. The "superego" is one of three Freudian personality characteristics. They are not specific or restricted to gender.
Do not confuse a common combination of adjectives (e.g. "Someone has a super ego.") with the specific noun coined by Dr. Sigmund Freud - superego - to define the personality characteristic that incorporates the morals and values of society.
Sigmund Freud's single most enduring and important idea was that the human psyche (personality) has more than one aspect. Freud (1923) saw the psyche structured into three parts (i.e. tripartite), the id, ego and superego, all developing at different stages in our lives. These are systems, not parts of the brain, or in any way physical.
McLeod, S. A. (2008). Id, Ego and Superego. Retrieved from www.simplypsychology.org/psyche.html
Freud, S. (1923). The ego and the id. SE, 19: 1-66.