how to get an S

i thought yasuo is easiler to get S, but i try so many times, and i got one time only, i just played a round, and kda is 11/0/4, and my cs is 290, and i got S- only. So, is there any other things i need to focus? And here's the site of my history: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2340856683/204118870?tab=overview