The two particularly promising models of high-mass star formation (M >8 Msun) are "monolithic collapse and disk accretion" and "competitive accretion" (Krumholz & Bonnell 2009).
The former suggests that high-mass stars form directly from isolated massive gas cores as do low-mass stars, but with a much larger accretion rate.
The latter claims that high-mass stars form in the center of a cluster competing for cloud gas with the other off-center protostars.
To distinguish these two models, high spatial resolution and sensitivity observations are needed.
I will talk about our recent works on observations toward high-mass star forming regions and also introduce our future observational plans.