Shower hot water valve still "leaking" after replacement of washers
I assume that this valve has replaceable "valve seats". Possibly the seat is worn and not allowing the new washer to make a seal. Remove the stem as you did to change the washer and look at the seat with a flashlight. If you see a notch or roughness, then the seat should be replaced. Put in a new washer too (or if it is symmetrical flip the washer) because the recently replaced washer will have gotten damaged by a damaged seat.

Use a valve seat tool to unscrew the seat and take it to a hardware store or a plumbing supply and get a pair. Install one and save the other for when the cold valve needs a new seat. Do not use Teflon tape on the threads of the seat. Even pipe dope is not necessary, but Teflon tape can cause a leak if a dangling strand of the tape ends up between the washer and the seat or even between the sealing surfaces. The threads on the seat are just a means of clamping the seat down and do not need to be sealed. The seal is made by the flat rim on the seat sealing against a flat in the body of the valve. 

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