It is possible to make a transfer from the master's program to the doctoral program (“fast track”), without having to write a master’s thesis.
This option is reserved for students demonstrating above-average ability, who are supported by their research supervisor and have completed the second term of their master's degree as well as all courses in their degree program.
For more information, please consult the following links (french only):
https://fas.umontreal.ca/etudes/maitrises-dess-et-microprogrammes/passage-accelere-au-doctorat/