I suppose you want to know how to improve band width and phase margin together. The main problem is improving one distroys the other, for example to improve phase margin you may add a compensation capacitor but this necissarily reduces your bandwidth
This effect is mainly due to that most of the methods used to improve the phase margin depend on reducing the gain to unity at the point when the phase shift between the input and the output is 180 - (required phase margin).
you may see Razavi (Analogue CMOS design) for further information. It has a complete chapter about stability and another chapter about Op-Amps